In late 1999 I claimed my last name as a domain, and have had various email and web solutions hanging off of it ever since. This past weekend I migrated off of self hosted email to Google Apps for Domains. My email address remains the same, but the infrastructure is Google's. There were 3 main converging trends that drove me there: spam, client innovation, and protocol integration.
Because most people host email on one of the big three (Google, Yahoo, Microsoft), spam fighting techniques for the little guy have largely stagnated. If you are big enough there are other algorithms you can apply to patterns affecting your millions of subscribers at once. For individual filtering, especially with an email address that's been constant for over a decade, the best you can do is spamassassin, which last released in 2011, and realistically hasn't done anything innovative in the last 3 years. So recently my false possitive and negative pool have been overlapping in a way that means a lot of manual work. Thunderbird's bayesan filtering is quite good, and makes up for some of this. So when my laptop is running while I'm getting mobile email, my spam rate in mobile is low. When it's not, about 80% of what gets to my mobile inbox is spam.
Spam by itself wouldn't have pushed me over the edge, but Mozilla deprecating new development on Thunderbird was another blow here. Email is powerful because it is universal, can be accessed by any device at any size, multiple clients interacting with the same data, at the same time. Desktop email has gotten the short end of the stick in recent years, again because most people are hosting with the big 3, but Mozilla was still making a valiant attempt to keep email open. They've now decided it's more interesting to chase Chrome than provide value here. That's their call, but it's sad to see desktop email take that hit.
Lastly, there are lots of quite interesting tools growing up to integrate with email in a new social world. Give you profiles of your contacts via social networks, make it easy to convert email into tasks. All great stuff. None of it works with IMAP or Desktop email. All the innovation around email right now is using the GMail API and Chrome extensions to modify GMail web interface.
So the migration is on, I've nearly got my email history dating back to 2000 into Google now. In the process I found I'd actually lost 2008 and 2009 archives, which I've mostly restored via backup. That would explain why some things weren't showing up in search that I expected. Already, the spam filtering is a huge win, and eventually I'll get used to the web UI for some things (still going to keep using Thunderbird in combo for a while).
The biggest challenge in this whole process is that because of how Google has wedged Plus into everything, having both a gmail and an apps email causes some real confusion on the Plus side, because there is no way to tell Google they are the same. That's just going to be confusing for a while, and if anyone has best practices around that, let me know.