It’s interesting to mention Evil Hat in this context as a company that makes money on RPGs, considering that their entire “Fate Worlds” line is PWYW. But then again, not ALL their works are PWYW. I am inclined to believe it’s a fine (perhaps even superior) pricing model for some kinds of products, but not necessarily ALL products.
I’m not especially concerned about the “slippery slope” issue—like, “anybody doing PWYW makes EVERYONE feel like they need to do PWYW”—as it certainly doesn’t feel like the model has caught on so fast that it’s overtaking traditional sales in this or any other industry. It might be overtaking downloads, if not sales, on platforms like Drivethrurpg, which seems flooded with games that clearly were not edited, proofread, playtested, or carefully laid out, listed as PWYW. But I don’t think that’s inappropriate at all. “Nothing” is a perfectly valid answer to “how much do you want to pay me to read my rough ideas?” I download that stuff for free all the time just in case I find an unexpected gem, and then toss the creator some cash when I realize what I really have. The rest of it is no more or less valuable to me than reading someone’s random blog (or G+) post about their ideas on gaming, so “free” sounds like the right price to me.