raising when first one in

[Maize]

I've had several people tell me now that in NL; if no
one has entered the pot; you should NEVER EVER limp;
ALWAYS either raise or fold. Some of them tell me this
is also true in limit; which; after 25 yrs. of playing
limit holdem;I don't believe to be true;unless maybe
in very late position and no one has entered.
Anyone have any constructive thoughts on this?