If the faction you have stocks in dissolves (like a rat in Pepsi) you get a payout based on your percentage of shares you own, other than that, it's a way for re-sellers to get greedy off of uninformed newbs
Especially since virtually every faction that dissolves is emptied before dissolution, reducing the payout to a hundred credits or so. (and the shares always sell for a lot more than the actual in game value so you'd draw a loss anyway..)