A stock price takes into account future growth. When growth begins to stagnate, then the ticker will fall. People lose money.

In most cases it probably isn't a huge deal, but the fact that Twitter isn't profitable is likely a (large) factor. Without a given amount of users, it won't be profitable and decreased growth obviously means that profitability is further out. Hence them cutting costs.

There's obviously nothing wrong with a bootstrapped / lifestyle business. The people at Basecamp are big proponents of it. https://www.youtube.com/watch?v=lBfVxBj61z0 Here's one interview out of plenty where they talk about this kind of thing.