Kent-
Though the RIAA is definitely tort-happy, I don't believe there have been any attempts to shut down online lyrics websites
Incorrect. The best lyrics archive of all time was lyrics.sh, and it was shut down via court order by the Swiss RIAA equivalent. I think they reached a settlement of some kind, but the site that is now in its place is a spam-infested craphole. Everything2.com, which is a bit like a wiki, has recently started to enforce strict copyright rules on material such as lyrics.
There are lots of ad-infested lyrics archives on the net, but it seems like the good ones always get shut down sooner or later. If you want to deal with legal threats, then go ahead and set up a lyrics wiki. Nowadays when I search for lyrics, I just google for a phrase from the song which I can identify (remember to put the phrase in quotes), that usually does the trick.
Regards,
Erik