Out of the 28 graffit-related charges the Suffolk District Attorney's Office has been trying to slap Shepard Fairey with for the last 9 years, only three stuck. And while the DA may be trying to hype the fact that Shepard did plead guilty in the end to three of those counts -- the DA's press release headline reads: "Fairey Pleads Guilty To Multiple Property Damage Charges" -- they were also forced to note the 25 other charges that didn't stick.
Okay, so Shepard Fairey's art involves defacing other people's property, sometimes with permission, sometimes without. He pastes his truly wonderful poster art on buildings, which are pieces of architecture, which is a form of art.
If he does this in Allston, people deface his posters. Tear out chunks and (since the shreds aren't scattered around the pavement, and we know nobody's ever swept that lot) keep them as souvenirs.