According to a post on the Twitter Status blog, the issue first showed a reduced number of followers on the service, and later, in order to solve the issue, Twitter went into a maintenance mode, warning of lower counts across the board. Amusingly, they claimed that some of the lower counts could be due to the removal of spammers, but in my experience, it's been more than 9 hours since the problem was first identified, and I've seen the number of people I'm following drastically cut, from more than 1,500, down to "only" 672, less than half.
On Monday, when I said "The Talk About Rules for Social Following Is Getting Out of Hand", I had taken a screenshot of my current Twitter ratio, at 1,534 to 1,441, after having worked for a good part of the previous week with Twitter Karma to get my ratio synchronized. Just a few days later, that data is carved to 672 and 1,236, prompting some to try and refollow me, and even more to flock to identi.ca.
Twitter's gotten a lot of abuse on this blog in the past few weeks, as we've gone over issues with developers, uptime and changes to the API, but every time I think they've captured the market on a single route to failure, they find another way.
The team's employees are talking a good game about getting this resolved, but seriously, Twitter, why should we believe you now?
Why Does Everything Suck: The Nightmare Twitter Scenario May Be Upon Us
Profy: So You Thought Nothing Could Be Worse Than Fail Whale? Now Get Your Followers Back