no all ins?

[tboneman]

Would someone take a few seconds and explain to me why pokerstars has nolimit tables with no "all ins" allowed? Im thinking of putting some money into that sight and was just nosing around to see what the tables were like when I noticed this "oddity". If your not allowed to go all in, how close to all in can you go? Any comments and or details on how this works would be appreciated.