Twitter's previously said it wanted to steer clear of patent litigation and focus on our feeds, but IBM may other ideas. In a tweak to its pre-IPO S-1 filing with the US SEC, Twitter let slip that it's recently received a letter from IBM accusing it of infringing three of the company's patents concerning: "efficient retrieval of uniform resource allocators," "presenting advertising in an interactive service," and "programmatic discovery of common contacts." There's no need for lawyering up just yet, as IBM would rather "negotiate a business resolution" -- or get paid off, in other words -- before lodging any legal complaint. Discussions could easily move from the boardroom to the courtroom, however, as Twitter also mentioned in the filing it believes it has "meritorious defenses to IBM's allegations." Oh well, here we go again.