http://www.thisamericanlife.org/radio-archives/episode/441/w...
Their explanation of the venue choice was that the other federal courts were choked with drug-related cases and going to East Texas was a way to get a speedier trial.
The America Invents Act changed this. Now the plaintiff cannot join unrelated defendants in one lawsuit, and so defendants have a much better chance of getting the case moved out of EDT. In face, since that provision of AIA went into effect, more patent cases have been filed in Delaware than EDT.
EDT actually is not particularly plaintiff friendly when it comes to results. There are several other districts where plaintiffs have a higher winning percentage than EDT. Last time I saw stats, a couple years ago, EDT wasn't even in the top 5.
The big attraction of EDT was/is:
1. The judges there are very familiar with patent law and patent litigation. Patent litigation is among the most complicated litigation, and whether you are a plaintiff or a defendant you want a judge who has experience with it.
2. There isn't a lot of Federal crime in EDT. Criminal cases have priority over civil cases, and in districts with a lot of Federal crime civil cases can suffer great delays. Try to litigate a patent case in a district where the courts are clogged with criminal cases (hello, war on drugs!) and you could be in litigation for a decade or more. Neither plaintiff nor defendant generally wants that.