[joosters]

It's a form of monitoring. Some update checks run whenever you start the program, so in the case of a program like f.lux, the developer gets to see exactly when you turn on and use your computer. Or, the update check might run periodically, in which case it's a constant survey of who in the world is running your code. That alone is a vast amount of information.

Also, many programs send a lot of details about your computer to the developer. They might send back hardware details, MAC addresses, lists of other running programs, and so on. All of which may seem innocuous but could still include personal information.

[kobayashi]

That's a great point.

You didn't say that you necessarily disagree with that monitoring, if you do, how do you feel about using Google Chrome, with it's near-constant communication with Google servers, looking for updates and alike?

[joosters]

I don't use chrome!