zshare
kudos on the domain.
Part 1. - I believe the key is to know the demographic, who's coming to your site? When these customers registered did they fill in customer info? You need a customer profile. I'd venture to say a blog community is not going to work because alot of them might be using the service for their myspace or tagworld community sites which are community based.
Part 2 - I believe the second part is to list all of the "add-on" services" that would appeal to this profile and the reason they found you.
If it were me, and I didn't have a product to sell I'd do a tutorial site maybe with user reviews to keep them clicking and throw in some adsense and become a reseller for certain products. We know that zshare allows for the upload of files, images, videos, audio and flash. So how about free tutorials, user reviews and your reseller links on imaging software, video/photo cameras, audio tools and podcasters equipment. I don't expect users that create flash to need this service but the flash tutorials are always being sought out too.
Think of it like a guy walking down the street to his favorite hot dog joint. He walks into your place that doesn't sell hot dogs, but you've got some cool stuff...exotic mustards, relishes, breads, ketchups, and a neat hot dog holder for when he's driving. He may not have been looking for you, but he'll be glad he found you.