Back when I was working on FeedLounge I suggested on more than one occasion that we needed an IMAP equivalent for feeds. This way, users could move between feed readers (mobile, desktop, online, etc.) and their read/unread status would be maintained between all of them. It’s interesting that Google Reader has basically become this solution.
In the last six months I’ve used NetNewsWire on the Mac and iOS, Scoop on the webOS and Reeder on the iOS – with an occasional visit to Google Reader on the web.
I still get uncomfortable that so much of the internet relies on Google, but I can’t argue with the convenience in this case.