[jedbrown]

You still have to prepare the application and pay some fees. http://www.uspto.gov/web/offices/ac/qs/ope/fee092611.htm

If a doubly-linked list is patentable, how many things have you built this month that are also patentable? Do you really have time to write all those bogus patent applications? In academia, it's a much better use of time to publish scientific papers, present at conferences, and put it in open source software. Industry has market-driven motivations.