I basically use Google for search, adsense, and mail service. The mail service is using their POP/SMTP servers (I don't use the web interface), so this would be very easy to switch to another provider.

So it would be an inconvenience for Google to go offline, but I could survive.

I don't trust anyone with my calendar after Excite.com ate my calendar many years ago (I have a big family, so there were a lot of dates in it). I now have a simple PHP/MySql setup for important birthdays and anniversaries – easily portable and very easy to back up. This had been in ASP/Access for several years, before I rewrote it to get away from Microsoft :) Well, mostly because MySql is free …