[mindo]

I doubt ads is the main source of revenue. They do sell DIDs, VOIP calls to landline phones and mobiles (with insane rates) so ads (only in few countries) doesn't account for much.

M$ bought lots of companies before, that eventually came to EOL even though they were doing pretty well before M$ bought them, it's not particularly about the skype (even though we see it gets worse over the time).