The post title comes from an essay by Georges Rey , in which he discusses what he calls the "philosophy fallacy":
The idea that one needs powerful philosophical theories to settle [whether there are gods, witches or ghosts] might be called the “philosophy fallacy.” [P]eople are particularly prey to it in religious discussions, both theist and atheist alike; indeed, atheists often get trapped into doing far more, far riskier philosophy than they need (247-248).
Indeed, Rey contends,
[T]he reasons for atheism are obvious, not depending upon some subtle metaphysics, or sophisticated theories of knowledge (of which, if the truth be known, no remotely adequate examples are available anyway). The errors in the standard arguments for the existence of God are ones that can be easily appreciated by anyone with an average high-school education (247). 
In my experience, Rey's contention bears out. I've never encountered a theological argument that (once I understood it, at least) didn't strike me as just obviously wrong. Even in a case where providing an exact diagnosis can be tricky (e.g., Anselm's ontological argument), that there is some kind of infirmity is manifest (in the case of Anselm's argument, for instance, that it proves too much).
And yet risky philosophy abounds in the philosophy of religion. There are many plausible reasons for its perseverance: Philosophical interest in some kinds of abstract arguments ; an intellectual need to address all possible, marginal challenges to one's views; a psychological need to rationalize one's current, settled views in the face of such challenges; a sociological desire to show that one's views are intellectually defensible; and so forth.
One thing seems near-certain, though: It can't reasonably be aimed at changing anyone's mind.
If you look among the testimonials posted at the Internet Infidels website, for instance, you'll find the authors cite various forces that moved them to apostatize: The evils witnessed in combat (Eric Tallberg); the gradual recognition of the apparent absurdities that abound in the Bible (Amanda Avellone, Farrell Till); the commonsense musings of general philosophers (Dan Barker); the plain contradictions between common-sense personal morality and the less-commonly advertised teachings of the Bible (Mark Vuletic, Ken Daniels, Kenneth Nahigian, Edward T. Babinski, Ian J. Carr, B. Steven Matthies); the dawning appreciation of science and the basic demand for evidence (Raymond D. Bradley, Robert M. Price, Kendall Hobbs; Richard Carrier ); the apparent conflict between religions (Clark Davis Adams); personal encounters with friendly, decent atheists (G. Vincent Runyon ); and/or all of the above. No risky philosophy there.
A similar pattern shows up in the testimonials contained in the Louise Antony volume : Stewart Shapiro's belief "snapped" when he heard that David Vetter died, having lived all but the final moments of his life entirely deprived of the touch of another human (3); Joseph Levine's aggregate doubts crystalized during college, when he realized he'd simply "lost all of [his] religious beliefs" (19); Daniel Garber's encounters with the religious traditions of others that suggested to him the arbitrariness of his own (35); along similar lines, Walter Sinnott-Armstrong was gradually struck by the inherent arbitrariness of the common Biblical narratives (72); key to Edwin Curley's growing incredulity was the unfairness of his church's embrace of the doctrine of predestination (80-81); Marvin Belzer came to rue the accidental quality of religious belief--that some will never even hear the stories, and others are constituted so as to find those stories incredible (96); and Louise Antony's gradual conversion came to a head in her first college philosophy class, a forum that finally allowed her the freedom do ask the sorts of questions she (and others) had anxiously suppressed all of her life (50-51). Nope, not there either.
What about belief change in the other direction -- in the direction of greater credulity? The situation there is even starker. "Conversion" experiences seem to be entirely driven by emotion, usually stemming from a personal crisis.  Take a gander at most any website that features testimonials from "born-agains," and you'll see what I mean.  There is very little room in the conversion process for even low-level intellection, and none at all for risky philosophy.
In sum, risky philosophy does not appear ever to have brought about even a quantum of belief change. You will probably search in vain for a (de)conversion testimonial that cites anything like, say, Goedel's proof, and by the time you are reading Quentin Smith or Alvin Plantinga, your views are either (1) pretty well settled or else (2) already on their way to changing without the help of Quentin Smith or Alvin Plantinga. When minds change, in either direction, it is in view of much more concrete considerations -- the problem of life's meaning, the problem of death, the problem of suffering, the problem of God's storied cruelty.
But all that means is that risky philosophy doesn't do any persuasive work at the object level. So how come it's "risky"? For an answer to that, you'll have to read Part II. Until then...
UPDATE: Continued at "Risky Philosophy - Part II."
1. Rey, G., "Meta-Atheism: Religious Avowal as Self-Deception," in Shapiro S., et al., Philosophers Without Gods: Meditations on Atheism and the Secular Life. Antony, L. ed. 2007. New York: Oxford University Press.
2. Parenthetically, Rey addresses a possible objection: "Of course, sophisticated versions of the arguments take sophistication to work through. But, naturally, the more sophisticated they are, the less likely they play a role in ordinary religious thought" (247).
3. In his essay "Reasonable Religious Disagreements" in the same volume, Richard Feldman observes, "I found the arguments about the existence of God philosophically interesting, but studying them did nothing to change my beliefs" (195).
5. I would exclude from the category of "conversion" a case like that of Antony Flew, not least because the view he currently expresses is a vague form of deism, which share any theological charge or therapeutic aim with mainstream religion.
6. See here, for example. It might appear that I'm loading the dice here by comparing the de-conversion stories of top philosophers with the conversion stories of (ostensibly less reflective) lay people. But the kind of visceral, anintellectual motivations you see described in the referenced site dovetail perfectly well with the conversion experience account of someone like William Lane Craig (at least as I recall his telling it; I don't have a quotation to hand). Besides which, the stats on conversion on their own appear to back up the strong claim that de-conversion is driven by intellection while conversion is driven by personal crisis and emotional need. See, e.g., pages 138-142 in Spilka, Bernard, et al., The Psychology of Religion: An Empirical Approach. Guildford Press. 2003.