@SE - Your situation is very interesting.
Yes, my site offers downloads, but only to registered paid members. Never in the past 12 years have I seen bandwidth that high for the day. What I've found so far is that my eth0 traffic (outgoing) saw a double rise ALL DAY yesterday, not any spikes as you might expect. Surprisingly, this happened on one of the slowest traffic days (real visitors) in months.
I just filed a reinclusion request the day before so perhaps Google was re-indexing me. Doesn't seem like it though, today is deader than it was before. The reinclusion prob backfired. I'll keep digging.