I just filled in the 2nd Annual Firefox Census, which is just a survey about weird stuff and Firefox and Mozilla and stuff (literally: like "To what Hogwarts house do you belong?").
I don't know why I feel like it's sort of okay to share data with a company like Mozilla, but I guess I do. Although, come to think of it I'll also sign up to loyalty programmes at grog shops too... I guess I don't really care about my personal information that much!
It's more the bloody annoying algorithms of YouTube and Twitter that annoy me. Give me chronologies and folksonomies any day! (Sort of. There is, of course, more to it, but that's always the case.)