[crunchy1]

There are many, many reasons why people sit at a table short stacked, get all-in, lose and then rebuy. What should be important for you is what range of hands they are willing to go all-in with when they're getting short. This is information that you can use to exploit their improper play.

Best advice - don't ever let yourself get in this situation. Make sure you always have enough chips to win the maximum when you have or flop a premium hand!