brent He gave some interesting statements yesterday, claiming Twitter was being "massively scraped" and something like there are "a ton of straws in this milkshake" or something thereabouts
Plenty of evidence posted online that it's probably actually because they made a change that the official Twitter clients (including the website) don't know how to handle, so they just keep retrying connections on failure indefinitely, thus DDoSing Twitter. Really can't trust a word that man says.