Most Common Reasons for Using OpenBC
Due to the fact that it was asked in an OpenBC group, I made a little list of the most common reasons for joining openBC:
Managing contacts
And OpenBC is a really good way to do that. Many options like sharing only selected parts of your profile or importing contacts.
Have a virtual replica of your real life social network
If they are already using OpenBC you simply have to add them to your network. Otherwise you can invite them to join the Club.
Finding new business partners
Well thats one of the reasons to be on the site every day. Using automated assistants to search for eventual business partners, searching the profiles, reading the groups.
Developing new ideas
By joining groups of your interest you can develope new ideas with the other members.
Sharing knowledge and interests
Another way to use OpenBC and its groups is to simply share your knowledge and ideas with others. There are many different groups for every imagineable subject. If yours is missing, just open a new group.
Vanity / Ego-monitoring
Who has the most contacts, is in most groups…
If you think I’ve missed an important point, feel free to post it in the comments…
Thx Tim for the additional last point! 
Vanity or ego-monitoring (ie who looked at my profile).