I agree, early on I stay more conservative due to people who will call all your bets with bad draws and hit them. Think about it this way: You limp in with Ac-5d offsuit and with the pot odds it's a good bet in some positions because that ace is sweet. the flop is As-5h-6h. Now you think, great! I just hit two pair. At this point you could be ahead, but then you could bet and get called/reraise by someone who also limped in with A-6 off suit (i've seen it happen to me and others a lot). Also, there is a good chance someone, especially the blind, might have limped in with 3-4 suited in hearts or even unsuited, 78suited/nonsuited, or A-7 or higher that could destroy you on that turn/river, or ATC that are suited in hearts and that person loves to bet on flush draws. It's great to think that you could get so much out of people because you limped in with some odd starting hands due to odds, but that applies to everyone else, and usually you'll have 3+ opponents who also limped in, thus the odds that the turn/river will make a hand that'll beat your two pair with that flop much greater. If you have less than 3 people in, limping isn't too bad of an idea, but remember that a lot of people like to go all in asap with a good-premium hand to get chip lead, and you might just see a lot of your limp bets forfeited when you get re raised by a large amount (many times close to all in) by someone in a later position than you.. To me, that's normally spells me loosing small chunks of chips quick because of those other possibilities (that are not usually unfounded unfortunately). If you're in late position you'll be able to see who's trash hand hit the flop, and it wont cost you more than the pre-flop call.
I like to limp in when i'm in very late position or in the BB of course, otherwise the risk is too great with a lot of people going in with anything. Even if you raise, raise a good amount; even if you raise 4x the BB, if its only 20, a lot of people will see an 80-120 chip raise as small compared to their 1500+ chip stack. Thus they're more likely to call with A-anything suited/unsuited, suited/unsuited connectors, etc.
I like to just survive the first couple blinds, only going in with a premium starting hand. That way, if I double up early then i can easily sit out and watch, and if I dont lose chips early, like it was mentioned above: when I do get a premium hand doubling up through the lucky high chip people will be easy, you might even triple up if you've got two crazy people who got lucky and have huge chip stacks call your all in, i've seen it many times before.
But then again, if you have a read on everyone then you should be able to limp in and be much safer, although not likely that early in the tournament.