Well, one use is you can access the contacts of your contacts, so it helps you get information about (and get in contact with) a lot of people...

But I agree it seems weird to add 50 'strangers' to your list... We don't know anything about each other really.

EDIT: Although I have seen a few people do it on LinkedIn already, they post message in groups and tell people that they want everyone to add them. They gather thousands of contacts that way, I wonder if it does them any good tho.