[mkent]

They look so fragile and beautiful - impressive they were able to get them in and setup without drawing any attention.

[lloeki]

He's most likely making use of an S.E.P field http://en.wikipedia.org/wiki/Somebody_Elses_Problem

[nickolai]

Nice reference, but your wikipedia link is broken (missing an apostrophe) :

http://en.wikipedia.org/wiki/Somebody_Else%27s_Problem

[goatforce5]

Banksy has hung artworks in high profile galleries and museums without being caught or subsequently identified:

http://gothamist.com/2005/03/23/museum_shows_for_banksy.php

[epo]

Amazing they weren't taken or vandalized TBH.