OK, so, as a native English speaker (and maybe specifically one in America), I generally try to capitalize "proper nouns", whether you have standing for a trademark or not... I thereby will happily talk about how "the App Store is an example of an app store" (though I also tend to disambiguate at least one instance with "Apple App Store", which, I think, certainly should be capitalized).

> Capitalization is the difference between "I had to help my uncle Jack off a horse" and "I had to help my uncle jack off a horse", amirite?