According to Tweetscan, an independent website which indexes and searches "tweets," the 140-character updates sent by Twitter devotees, the two were discussing Twitter on their ABC talk show, The View, right before Twitter failed.
The outage is unusually severe: Twitter's website is wholly unavailable, unlike past incidents where Twitter displayed an error message known as the "fail whale" for the whimsical cetacean it displayed. Whatever the cause — overcapacity induced by The View's large audience hitting the site all at once, or an inconveniently coincidental outage — it's an embarrassment for a site which had pledged that prolonged outages were a thing of the past.
The last messages displayed before Twitter went down:
Update: Our long national nightmare is over! Sort of. Twitter.com is available again, but the site is displaying the fail whale: