What have people found is the best way to 'crowdsource' knowledge about a collection of hundreds/thousands of family photos among several generations of extended family with widely varying (but on average low) technical ability?
My husband and I have tried many ways, with numerous sets of photos and different families. What's been most successful for us is starting a private group on facebook, that no one uninvited can see or find. It is very private, and that's been good, as it let people feel more free to express their feelings and tell stories that they wouldn't want anyone outside the family sharing. The more people we got to look at the photos and comment on them, the better the system worked.
In our case, these were the photos and papers left by the youngest daughter of 11 siblings who had nursed her mother and many other siblings as they died. She ended up with six sets of photos and papers, including her parents. We wanted to share them with all of the grandchildren and great grandchildren. This worked for us.
(1) any way to import metadata (descriptions, etc.) from an existing source or does it all have to be reentered by hand?
Not on facebook, that I found. I scanned and uploaded the photos and papers. Everyone was free to comment on them. The comments and stories sometimes went well afield of the photos, which was all the more interesting.
(2) Any tips on structuring descriptions so as to be able to search accurately (eg "Bella Poland 1920s" etc.)?
We uploaded them starting with albums, and labeled as such, including any labels for individual photos or papers. By putting each persons facebook name in the description, you could limit your search by person. This doesn't help you for years, or places or such.
(3) I read that there are issues with exporting comments should we ever want to move to a different platform. Any thoughts?
I've thought about this, but not come up with a good answer. I'm not sure that they can be exported at all, unless by taking individual screen shots.
The main advantage of facebook over other methods that we've tried, is the ease of use for the extended family. Any of the cousins that have a facebook account can fairly easily learn to navigate this system. There were some that don't have facebook accounts, and don't want one. They can't use this, unless they ask their children to show them. Most of the family though already had facebook accounts, and so this worked easily and quickly for us.
Another advantage of facebook is that they will notify the family, via email, when new photos are added to the library, or a new post is add to one that you've previously commented on.
It's not a wonderful system, but it's worked very well for us. We probably have about 5000 photos, papers, awards, telegrams, newspaper articles, pieces of jewelry, etc posted to this site.
Good luck to you!
Memphis, Tennessee, USA