That kind of business model is: winer takes all.

For every niche, there would be only 1 winer makes money, 1 survivor hanging above break even line, 1 slightly below water wishfully thinking... everybody's else dead already. You have to run for the speed first.

Each story can't last long either, like the Groupon / Living Social, WebEx / GoToMeeting, My Space / FB / Monster...

Good thing about segmented business, like landlord here as a good example, it's easier for people to start and last longer. 小而碎也有好处，大鳄也不容易整合。要是没有那实力，就不能处于四战之地。