Dunbar's Number - the number of people with whom one can maintain stable social relationships
One can tell that it isn't actually science because they've only managed to narrow it down to somewhere between 100 and 230, a ridiculously vague range.
Assuming, however, that there is some validity to the theory, I would seem to have room for between 80 to 90 and 210 to 220 more stable social relationships. That's a lot of people. I don't know if I even want that many people in my life.
On the other hand, it does say "can" not "must".