Watch the Level 5: Blues Bends online guitar lesson by Jeff McErlain from Take 5: Blues Bends
String bending helps emulate the qualities of the human voice more than an instrument like a piano can. I'd say traditional jazz guitarist don't usually bend strings that often, as those jazz boxes usually have very heavy strings on them, but every one else usually does.
Here are some guys who's style is identified with particularly creative bending: Jeff Beck in my mind is the king. There's also Roy Buchanan, Albert King, Otis Rush, BB King, Eric Clapton, and Jimi Hendrix to name a few.