Why did facebook block me for adding friends?

[Catbat]

I've been temporarily blocked. However, I really do not think I'm abusing the system. I was late on joining the FB bandwagon and now that I'm going off to college, I'm trying to add as many people from my HS (as well as friends from outside it) before I'll be too busy to remember. I got to about 200 friends and then facebook temporarily blocked me and this message comes up whenever I try to friend someone "You’re Temporarily Blocked
It looks like you were misusing this feature by going too fast. You’ve been blocked from using it.

Learn more about blocks in the Help Center.

If you think you're seeing this by mistake, please let us know."

They did warn me beforehand to slow down, and I did! I only added a couple more people and then facebook blocked me. What bothers me is I was adding people from my high school, and we would have mutual friends. I don't see the problem with adding people so quickly (as well as adding people from your email and phone contacts). Is there a way I can explain to facebook that this is unfair? And if this happens again, will I be permanently banned? Now I'm afraid to add people when this block is uplifted.

Thanks.