Ugh, really? I use Dropbox for personal photos, as well as a shared space for some work stuff. I thought that it only counted against one of the users.
They are absolutely right about how shared folders could be abused by non-paying customers. For example you could create ten dummy free accounts and make them all share with your account, and then have lots of storage. That is why they count your own and shared for free accounts.
But they do the same counting for paid accounts even when all parties involved are paying. No amount of discussion with support would get them to even acknowledge the issue. If you go into your account settings you'll see the bar graph and details of how shared files are being counted against you.
