Looking for some suggestions on my Undergrad Art History thesis topic, any takers?

I’m writing my undergrad thesis on contemporary graffiti and street art, and for those who are familiar, which artists turn you on and why? What is being said on the walls of our urban environments, and what do you think is their greatest influence?
Any purists out there, what do you think?

…sorry, this question is pretty heavy!

EDIT: Oh, and for the sake of avoiding a lot of redundancy and argumentation here (which has been brought to my attention from previous posts), I’m actually analyzing the visual culture of the images being created, NOT whether its vandalism; that has already been argued—to death. More or less, I’m looking for an audience’s response to new street art media beyond just tagging, i.e. urban renewal, reverse & light graffiti, pedestrian disturbance, spatial projects.

The subculture has evolved drastically even within the past 6 months, so instead of the normal run of the mill argument, I need an general audience’s response to what messages contemporary works portray, and how they have become a staple of our socio-visual and popular culture.

Suggestions of lesser known artists would be appreciated, as well as any casual analysis of imagery and content!

SO, with that said…any insight?