Creative Commons defines a CC0 license type (here's the full legal code) that claims to allow creators to release their works into the public domain by waiving "all their copyright and related rights in their works to the fullest extent allowed by law."
They claim in their FAQ (and the FSF confirms) that CC0 is compatible with the GPL, which is approved by the Open Source Initiative (OSI) for use with software. However, OSI has not approved CC0 and does not recommend its use as an OSS license (emphasis mine):
The most serious of the concerns raised had to do with the effects of clause 4(a), which reads: "No ... patent rights held by Affirmer are waived, abandoned, surrendered, licensed or otherwise affected by this document.". While many open source licenses simply do not mention patents, it is exceedingly rare for open source licenses to explicitly disclaim any conveyance of patent rights, and the Committee felt that approving such a license would set a dangerous precedent, and possibly even weaken patent infringement defenses available to users of software released under CC0.
I'm not sure I understand the basis for concern here (or why CC0 includes this clause to begin with, but that's another issue). I understand that you can't make someone else's patents available by putting code that utilizes those patents into the public domain, but the clause specifically refers to the "Affirmer's" patent rights (the person who decided to release the code in the first place).
What evidence is there to support the idea that using code released under CC0 would ever result in infringement of the author's own patents? I'm looking for a specific example to illustrate when and how this could ever be a problem.