Everyone's being targeted. GetJar is undoubtedly receiving data from millions of phones, not just yours - you only
noticed because you're a developer. GetJar has no idea you're a developer, and if they did, they wouldn't care.
The 'spy on currently developing apps' thing is a nice-sounding theory, but it's wrong. I've worked extensively in this industry (although not for GetJar), and the only developers any company in this space is interested in are the ones that are already moving a ton of units, not ones working on applications that statistically are unlikely to see the light of day or make a single sale. And they're only interested in the big developers because they want to sell them some advertising or get them to run ads in their apps. The money you can make from advertising is huge, while the money you could make from some sort of corporate espionage is tiny. (How would you even sell it?)
The data collected is almost absolutely related to ad targeting. The advertising company fetches a list of installed applications, ignores all the stuff it knows nothing about, and uses the rest to construct a profile about what you like which it can use to show you better-performing advertisements. You use Fandango? Great, we'll show you movie ads. You play Cut the Rope a lot? Great, we'll slot you into our casual gaming segment, and show you casual games.
There's still plenty to object to, if you like - sticking this in a paid game is kind of lame, even if they did disclose it - but it's not at all what you think.