Sunday or Monday, there was a post on AR15.COM with over 200 billion replies! It slowed things down to a crawl.
There was some disagreement over whether it was a software glitch, or sabotage. I have no idea if the current outage is related to the incident earlier this week.
I emailed Ed, the site owner, on Wednesday, but he hasn't replied, perhaps he's too busy, and that's understandable. It's unusual though, that no word has gotten out to anyone AFAIK about what the problem is. If I learn something, I'll post it here.