[pzhon]

Most hands are not strong enough to enter a raised pot with no discount. (Limping hands would be happy to get a 50% discount, which is why if you limp, you should call one more bet from a raise behind you.) A common leak is to cold-call with a hand worth limping. This costs significantly less than 1 SB (out of the 2 SB put in) but the pot is often large, so many losing players don't notice how bad it is. It is a serious problem because it is a mistake that can be repeated often.

Hands that are strong enough to enter a raised pot with no discount are often better off 3-betting. This applies more pressure to the blinds and limpers. It's quite possible that you and the original raiser have an equity edge over the other players in the pot and are both happier to put 3 bets in whether your opponents call or fold.

In NL, it is much more commonly correct to call a raise (and much more commonly correct to limp and then fold to a raise). The raise is larger, so there is no need to 3-bet to add pressure to the blinds. Position is more important, so you may enter the pot with no discount even if you think you are behind the raiser's range of hands. Reraising lightly is dangerous, since it may be very costly to let preflop raiser act again.

There are some hands and situations in which it may be right to cold-call in limit when many players wouldn't. Many people are familiar with the idea of cold-calling with KQs, AJs, and AQs, but in some circumstances, I believe it is right to cold-call with AK when you feel you would have a more significant equity edge in a multiway pot.