Thanks dloft, I appreciate the response. I know you can't really answer why _I_ got rejected, I was just curious if there was something in particular they were looking for. Applying to companies and getting rejected tends to give very little feedback, and I'd like to know what I should be focusing on improving. I guess that's kind of par for the course though.
Sorry, I can't say why you specifically didn't get an interview. There are a lot of factors to consider and a lot of candidates. No recruiting process is perfect. If you're really passionate about working at Twitter, please re-apply and include a cover letter. cc me if you feel like it (dloft) and I'll make sure you at least get a response.
Twitter is really a great place to work, filled with smart, productive, passionate and unabashedly quirky people. If you're one of those, I sincerely hope that we hire you.