As you may remember, Google made HTTPS a small ranking signal and many SEOs and webmasters flocked to switch their sites to be fully HTTPS. Heck, we moved this site and I also moved my corporate site - mostly so I can report back to you on the success or failure. I saw none in terms of rankings in Google.
And since most webmasters saw no ranking changes, some are considering switching back from HTTPS to HTTP.
A WebmasterWorld thread has one webmaster asking what should he think about when migrating back? It would be the same concerns you need to think about when migrating from HTTP to HTTPS minus worrying about your SSL certificate not working or having content mismatch errors. In fact, switching from HTTPS to HTTP is way easier than switching from HTTP to HTTPS.
Why is he switching back?
(1) don't really need https for an informational website
(2) don't see any ranking nor trust improvement
(3) browsers block http images, http iframes, any kind of non-https resource included in my websites.
(4) probably server load is higher for https (not tested)
Those are his reasons, and you can argue with number one, you can solve numbers 3 and 4 but number two, no one would argue with.
I suspect most people who switched are not switching back? Right?
Forum discussion at WebmasterWorld.