YMMV, but people talk about these ads firefox is throwing around and I just don't see them. Did I accidentally turn a knob or something and it's just carried with me through years of Firefox Sync'ing?
I see the fresh installs often because I only use Firefox to test occasional browser bugs (it's always Firefox), and then delete it a few weeks later when I no longer need it, then reinstall it later when I need to test it again. Every time it gets more annoying.