It really depends on the situation, for example in the mid-late stages of tournaments with antees in place which usually adds up to another bb your pretty much committed to call. eg blinds at 1000/2000 antees at 200 if you have 100k chips at 10 handed table and someone moves all in for 3bb and your looking at 76 suited then if everyone including the small b folds you have BB plus SB=3000 plus antee= 2000
2000+3000+ his raise which would be 6000=11000
you have to call 4000 to win 15000
thats almost 4-1 odds
your been offered so you would show a profit calling in the bb with any two cards in the long run and your healthy stack won't hurt you much to call, it is definitely a mistake to fold.
conversely if you are sitting with 16000 chips blinds are at 500-1000 and no antes and your in the bb and someone raises all in to 4000 chips making the pot 5500 you have to put in 3000 more to call your been offered 3000/8500
which is almost 3-1 to call so basically there is no situation in poker when 3bb all in is a negative equity call assuming you don't know there hand.
however I wouldn't like to call this off when losing the hand would leave me short stacked.
how close you are to the bubble and the values of different prizes can drastically alter this to.
for example in sit and goes there are situations when you have the pot odds
to call all ins But doing so would be a mistake for ICM reasons.
ultimately it depends on structure and situation but as a general rule I would advice never to fold anything but complete junk with a stack size of 20BB+