SPAM is a general problem with email. I assume that "for fun" emails sent to people I know will not be considered to be SPAM :-)

I don't want to say spam is a solved problem, but at least with gmail, I haven't seen anything spam-like hit my inbox in at least a month.

I think, there are some good spam-filters out there.

Gmail as replacement of FB is a little troublesome solution, I think. Gmail also has his privacy problems, though absolutely not as huge as Facebooks. I think, own (challenging) or paid Mail-providers should be preferred if you really want more privacy. Paid Mail-providers should be able to do the spam-filtering for you.

I'm seriously looking at Fastmail rather than Gmail. Once they get CardDAV / CalDAV support out of development, I would consider them a serious contender.

FYI, our CalDAV support has been in full production for almost a year now.

I was referring more to them as a pair. I know that CalDAV has been out for a while (didn't know it was production, thought it might still be beta), but I know that CardDAV has been taking longer due to integration with your pre-existing contacts system. :)