I'M GLAD YOU ASKED. There are two aspects of Twitter that just bug me as an engineer:
Blërg solves these problems by applying absurd reactionary engineering. Blërg's database backend is a custom C program that handles requests over HTTP and stores data in a very small and efficient indexed log-structured database. The frontend is done entirely in client-side Javascript. A single post can be up to 65535 bytes in length.
Which is not to say that I believe writing your service in C is the solution to all your problems. Clearly, this approach has just as many hairy problems that will bite you in the ass sooner or later. The best way, as with most things, lies somewhere in the middle of high-level abstraction and ZOMGHARDCORE OPTIMIZATION.
Yes. No. Maybe. Blërg is an exercise in constructive satire — a fully functional service created in a fit of hubris to poke fun at Twitter's engineering. It's just for fun, but no one is going to keep you from using it seriously. :]
Here, take a look at the design docs.
I've created a bookmarklet just for you: Blërg it!