Some shorties will be there cos they just dont know BRM and are fish, and some will be purposefully buying in short and playing a shortstack strategy. Its the latter that are more of a problem. Try and distinguish between the two different types.
Yep, always check to see if the short-stacker actually knows what he's doing (can be tough to play against) or if it's just one of the old fart degens that haven't bathed in a week that have scrounged up the table minimum from under the sofa and are hoping to get more beer money.
Presuming they are following the SSS and MSS detailed on http://www.pokerstrategy.com/strategy/sss/#basic it's often AJs, AQ+ and JJ+, but it varies according to the action in front of them. If one player limps, and another raises, the 40bb shortstack usually has AK (or QQ+) when he 3-bet shoves. (There are more combos of AK than there are of pairs, which is why you'll see AK more often than not).
I sometimes short stack in 100nl 30bb (No not hit and run)...and it depends on the villain. Probably 1010+, AJ+...sometimes a bit tighter depending on table dynamics, villains stats and stack size etc.
Also...I don't like to shove over an initial open, too much lost value here. I would prefer to 3bet/fold or 3bets call to shove once again depending on the situation.
