I have been blocked from sending facebook friend requests...why?

[Raoul Duke]

Don't Add Too Many Friends
Yes, it's true, Facebook has banned members for adding too many friends, or at least for adding too many friends "too fast." What's ironic about this is that Facebook makes it possible for you to invite a bunch of people at once by importing your address book. If Facebook decides you have a ridiculous number of contacts, you could find your account disabled.

Apparently Facebook has also banned people for being too active. If you spend a lot of time writing on your friends' walls, it could trigger Facebook's spam alert.

To avoid problems, you should only add a few friends at a time. Don't be too post-happy. Try not to be too popular.

Supporting links:
Popular Recruiter and Blogger Gets Banned: If you have a lot of contacts in your address book, this is a good example of why you should think twice about importing them all to Facebook.

Free the Blackadder one! A union organizer is banned for adding too many friends.

Facebook Ban: Banned From Inviting Friends and Sending Messages: Another blogger gets the Facebook backlash.