Nothing more than saving us the manual work, and perhaps offering a little more continuity since humans (especially me) are not particularly consistent about routine tasks. The alternative is indeed to do it like the rationality quotes threads, make it a community effort. But why make people do a computer's work if they don't have to?
Time to crunch some numbers: ~250 sequences posts at 5 minutes each makes 20 hours of work in reposting the sequences manually.
Since you reckon this could be done by two people in a day, I guess that's less than 20 hours' work: added to the fact that writing the bot is almost certainly more fun than copy-pasting the sequence, it looks like the bot gets my vote.
So, the London community is arranging a Hackday where some of us will get together and code. In order to ensure we work on the awesomest idea(s) possible, we decided to ask LessWrong to add to our list of candidates. So here is the question:
What could a few developers do in a day or less worth of coding that will be awesome? Also, as a way of checking calibration, you can give your estimate for how long such a thing would take to build.
Note: While we will take ideas and voting here into account, there is no guarantee that we will actually end up choosing one or more of them.