Me personally, it depends on the player sitting beside you. And what kind of player they are. For instance a tight player you should raise. If he folds, you scrape the pot. If he RE raises, you fold. Also the chips stacks may come into play as well. So you have to watch out for that as well. I'm not a big fan of limping in. You don't really gather any information like that.
There are obvious pros and cons to limping from the SB. In a pot where it's been folded around to you, the BB may see a limp as a sign of weakness and come back over the top of you. In the case of a multiway pot, your chances of winning the pot decrease with each player that enters the pot.
Well a lot of my reasoning for limping is the pot odds preflop in a multiway pot. If 5 people have limped and one in the big blind with blinds at 10/20, that's 130 chips in the pot. It would only cost 10 chips to win 140. I'd call every time even though I'd be risking the big blind raising or whatever. It's simple math to call there with any hand IMO.
On the other hand, as atlantafalcons0 points out, with each limper that comes into the pot, your pot odds increase which may justify a call with ATC. Looked at simply, it's a small risk compared to the potential reward especially when implied odds are taken into account.
I personally prefer not to invest a single chip into a weak hand. I've had people complain that I don't complete my small blind often enough. Oh well. Each chip I save now is that much more someone is going to have to pay off when I eventually double up. At the same time, because I already have chips invested in the pot, I do tend to use my BB and SB as an excuse to play hands that I might not normally get involved with. Because I don't show a willingness to play ATC from the SB or an interest trying to steal from the SB, when I do decide to play from the SB it's almost as if my limp carries the force of a raise and I am often given credit for a much stronger hand than I am actually holding, giving me an advantage in post-flop play.