After thinking this over a bit more: does this mean every forum page would require connecting to BPIP.org up to 20 times? If I understand the current extension correctly, it doesn't require anything from BPIP without clicking the link.
I don't know about the BPIP extension but technically it doesn't have to be 20 requests. It should be one request containing a list of user IDs, 20 or less because there can be duplicate users on the page and the ban status can be cached across pages as well.