Right now, Twitter is suffering slowdowns. Earlier today it was down again. :(
There are an excessive number of single points of failure in the current system, and through developer error* and external circumstance we have managed to hit quite a few of them in the last week. I am sorry and embarrassed.
In particular, we mis-estimated the impact of some cache policy changes. If your site runs so hot that it can’t function without memcached, you’d better understand exactly how much buffer capacity you actually have.
We’re working on fixing it all, but it takes a long time…
* I ain’t sayin’ it was me, but I ain’t sayin’ it wasn’t.
evan weaver 
Thanks for the note. Twitter definitely could use more transparency as you guys work through issues, so its good to see posts like this.
Yeah, I agree re. transparency.
There have been some awesome solutions proposed on the official blog about how to fix it:
I want to leave a blogger comment here, too.
Chris: You can, but it has to be HUGE and UNUSUAL.
@evan
Your humor is encouraging :)
Feel free to email me about the post I made to the mailing list. I know it was ambiguous (on purpose).