So, you're saying that people are, in effect, building lottery tickets when they create start-ups? Is no one interested in building businesses anymore?

This how it works with VC funded companies, you either need to sell them or go public. The VCs need to get a return on their investment. Since there are only 1,000 companies or so going public per year, selling to another company is your best bet. And if you do that you might as well do so for the best possible price. I don't think this is bad per se.

A team of good programmers is valuable in its own right, unlike a lottery ticket.

How does a company being bought for talent work exactly? If I join a company that gets bought, how long am I usually legally obligated to work for the company that bought my current employer?

There are a number of issues at play here, but short answer, you are not legally obligated to work at all, you can leave any time.

With that said the issues involved are as such:

1. If you had equity in a company (and sometimes even if you don't) it is not uncommon to sign a non-compete contract as part of the sale that bars you from working for a competitor for about a year. 2. Often, much of the value of the sale for employees is structured as retention payments, i.e. they set up a number of bonuses that are spread out over a few years, and you need to work at the company for that duration to get those bonuses.