I've only seen people move to postgresql (generally from mysql). I've never heard of people moving away from postgresql. Granted, that's a small sample size.
Etsy did. I don't think it was a good decision and I think the reasons they did had more to do with resetting from some bad architecture decisions, but they're the example I know of. http://codeascraft.etsy.com/2011/09/28/scaling-etsy-what-wen... I think the big lesson here would be: don't have separate DBA and Engineering teams.
On the other hand, I could name quite a few people who went the other way, like Urban Dictionary who run on our http://postgres.heroku.com service, too. (I don't normally name customers, but he recorded a video saying he liked us so I think it's fair game. http://success.heroku.com/urbandictionary )
On the other hand, I could name quite a few people who went the other way, like Urban Dictionary who run on our http://postgres.heroku.com service, too. (I don't normally name customers, but he recorded a video saying he liked us so I think it's fair game. http://success.heroku.com/urbandictionary )