Ok so facebook groups have 100,000's of members. Members can be part of an unlimited number of groups, and a group can have an unlimited number of members.
Comma Deliniated String seems absurd. Many-2-Many Database relationship seems like it won't scale well t the 10's of thousands and 100's of thousands of members (especially if you have 1000-5000 groups). A table for each group would work but thats a bit over the top in my opinion. XML file doesn't seem to be any better than the above options.
I am no database guru, but I can't figure out a scalable method of doing this, be it with or without a database. I need something that can support 10 groups that have 20 members each OR 1000 groups with 100,000 members each.
Any help, suggestions, or kicked in the right direction would be most appreciated.