A negative effect, most certainly. While some are masked as being geared toward creativity, such as Project Runway and those kind of fun cooking shows, at the end of the day it is the drama which draws us in. I won't lie, I'm fully addicted to Dance Moms, and from time to time I have been known to rot my brain with Jersey Shore, but it is the drama that reels me in. I use the defense that I like seeing the routines they they come up with and the like, but it is the drama.
This has a negative effect because it tells people that it is ok to be as confrontational, sneaky, defensive and catty to the world around them as these people are on TV.
We should be working on perfecting and improving our own lives instead of judging and getting sucked into what other people are doing. It's essentially also living vicariously through other people. One can see what it's like to race around the world on a massive scavenger hunt from the comfort of their own home, with minimal effort and virtually no funds. They could watch it, or they could actually go and do that, see the world, enrich their minds, and get active!
But I suppose the same could be said about all television too.