It's wishful thinking. People love to think they have more influence over the destiny of corporations than they really do. And, of course, the media loves to pile on.

Sure, voting with your wallet, when done en masse and over a long period of time, can have a significant impact. But this takes much more than a few days.

What UAL did in this case was horrendous, but trying to associate it with loss of market cap is disingenuous. The market always corrects itself after the initial fluctuations. It will depend primarily on their earnings on Monday [1].

[1] http://finance.yahoo.com/news/united-continental-ual-q1-earn...