Legalizing something can have myriad benefits, from improving product quality, to...to...oh man, so high right now. Taking online sheet music above ground, UnitedWeTab.
From a musician/techie tired of unlicensed tablature loaded with egregious errors, UWT aligns the goals of artists and amateurs by purchasing vetted sheet music directly from publishers and recouping the cash via an iTunes-like download model, which hopefully will stand the test of time better than Kelly LeBrock. Currently boasting 13,000 (and growing) songs by artists from Beethoven to B.B. King, each download features both standard notation and tab for lead/rhythm guitar & bass, plus a tempo-adjustable MIDI file that plays the correct rhythm, which you can use to learn a part or simply look into the future at Robotic Eric Johnson (if you don't know who that is, go jump off the Cliffs of Dover...G3 RULES!). They also assigned 40 musicians to record video tutorials, with one player handling both lead and rhythm roles, which're then shown simultaneously using PIP technology (cause you never want to miss when the lead guitar scores a go-ahead touchdown).
To top it off, anyone who signs up for a free account can keep a library of favorites directly on the site, a good thing as it isn't easy to find "Purple Haze" tabs when you're all hopped up on it.