I had the same thing happen on both Facebook and Twitter. The answer is: nothing.

In both cases for me, I had signed up and logged in for the first time, and was met with an immediate ban. No rhyme or reason why.

I, too, needed it for work so had no prior history from my IPs in the case of Facebook at least. So maybe that's why, but still. Very aggressive and annoying blocking algorithm behavior like that cost them some advertising money as we just decided it wasn't worth it to even advertise there.