"Manipulating and Exploiting" would seem to be the key phrase here, and most of the time I would have to say NO. Like Pohnpei said, the people who sign up for realities shows generally know what they are getting into and people who watch the show can always turn it off. To me, being manipulated has the connotation that you don't really know it is going on...most people, by now, are sophisticated enough to know that TV producers are going to get what they can out of you and watch the shows with a grain of salt.
That said, I have seen certain reality shows that may cross that line (and even here I wonder if the people involved don't at least suspect subconsciously that they are being exploited.) Reality shows that deal with washed up celebrities (Gary Coleman running a restaurant for cash and prizes,) recovering addicts (like you see on TLC all the time), or children (remember that Fox show where the kids ran the town?) I think are exploitive.
Some are manipulative to the "actors" (I'm thinking of the Joe Millionaire show, where they trick the girl into thinking he's rich when he's really just fat and balding.) I can't really see, though, how the audience is being manipulated in a truly negative way (beyond having their emotions toyed with by characters they come to care about.)
At least, that's my two cents.