Once a concept is described in print, it is available to anyone defending against a charge of patent infringement and that is a sure defense. One person to whom I suggested this course of action responded that the kind of software techniques he was concerned with were too elementary for prestigious journals. This could be true, but the evidence does not depend on the quality of the journal. Elementary articles, popular magazines, how-to courses, everything can count as prior art. Somewhat related to prior art is obviousness.
Prior art proves someone did it before.
Obviousness says anyone could have done it. This is clearly more a matter of opinion than prior art, but they are often closely related. For example, a patent may be rejected for obviousness because the patent examiner thinks, or the alleged infringer successfully argues, that it is a simple enhancement of prior art or the obvious combination of several pieces of prior art. An argument put forward against the current crop of software patents is that too many obvious patents are granted. That is, patent examiners are not sufficiently well versed in the current practices of software and too many patents are being granted.