I think the topic of limping should be viewed in respect to your own ability to play post flop poker as well as whether or not you have a plausible reason to limp.
1st off, post flop poker is much easier if you have gained some info preflop. And limping will get you virtually no info whatsoever. So limping will often make postflop playing a shot in the dark, which is mostly not a good idea. Still, in certain situations, limping is a very legitimate play.
As I said, it depends on your poker skills, and - IMO very important - the reason you have for limping and what you expect to happen. i.e. how you plan to continue on all possible scenarios.
One example of when I think limping is better than raising. Of course, I am assuming how the players will react to my limp, and if I am wrong, then I need to reevaluate.
I am in EP with a raisable (how do you spell that..lol) hand like KQs or w/e. (raisable hand ranges vary depending on your table). I know that there is an agro player in the SB/BB. I also know the rest of the table will have 2-3 people who almost always limp behind but fold to a raise. I want to play this hand, and I am fairly sure the agro player will raise it for me. So I limp, and depending on how I want to play vs the agro player, I can call his bet (this will be very read dependent, and I will have to know how he plays post, so I can make my plan now) or just now 3 bet him.
Scenario 2: You have 1-2 players with FPS. You have seen them limp behind with AA-QQ, w/e. They love to do this and go crazy post. Limping small PP is a great idea here. OC you have to be reasonable sure no squeezers are in position to fuk u up. I know people will argue this like "Why not raise, and trap him (them) in a bigger pot" etc. But vs these players you are fairly certain to GII post in any case, and you also have the added "limp behind" players who will fold to a raise.
There are other scenarios, however I need to stress the point that a limp as PART OF A PLAN is certainly legitimate. Limping cause you want to see a cheap flop is not a good reason. Limping behind when you have a lot of players in the pot can be very good with marginal but potential hidden monsters.
The things I mentioned are rampant in the micros. I limp vs agro players in the blinds a lot from EP and when they raise the 3 limpers that followed me, I fire and they fold. OC, you can only do this a couple of times b4 they fight back, which is also part of the plan, if you see what I mean.
Main point, have a reason for everything.