dis·in·gen·u·ous –adjective lacking in frankness, candor, or sincerity; falsely or hypocritically ingenuous; insincere

Use in a sentence:
You are being disingenuous if your Twitter bio says you are one thing, and your tweets have absolutely nothing to do with that thing, but are obviously paid tweets for something else.

Addendum - 11/25/2010
You are also being disingenuous if your first DM to "welcome" someone who has actually taken the time to look at your profile and Twitter stream is a click-through come-on.

I don't mind being sold to. I do mind being used.