Haven't played online long and got my start live as well - so take this for what it is worth...not much.
Online: I notice it more in freerolls
or play $ games than with cash...what would you expect when the game means little financially? Not everyone is a poker purist. When it occurs in cash games or tourneys, I am guessing it is partly because of a certain detatchment from the online deposit the player made and partly stupidity.
Live: Most of the people I play live with are far from donks. And, there $ is usually close by to remind them that the chips actually mean something - Thus producing a bit more conservative calls. But I have never played in a live tournament either...just friendly (or not so much) tables of 6 or 8.
again..just my observation.