I was taught to always raise when I'm first to enter a pot.
Any general poker advice that begins with "always" is probably bad advice.
Just think before you act. If you are open limping in to a pot you should be thinking how do I make money by limping here? What are the players acting after me likely to do here? Am I going to call a raise? Am I going to re-raise a raise? etc.
As long as you have a game plan that is though out before hitting the call button, I don't mind limping in sometimes. I have been at tables before where the person after me ALWAYS raises on the button if there are limpers because he gets position against someone that doesn't have a great hand. So I might limp my top hands to get a raise and a call from either the SB or BB and then 3-bet large preflop.
I'm not saying by any means that's the only way to play it, but I think as long as you have a smart plan going forward and you actually have a plan that you think in the long run makes you money, then it's ok.