The following article was recently posted, which primarily just prints
out opinion and analysis of Microsoft patents as has been discussed at
mxcomp. But of most interest to me, was, the kind of answer Microsoft gave,
which directly concerns SPF, see below:
http://www.internetnews.com/dev-news/article.php/3409971
...
Microsoft would not comment on specifics of the patent application but a
spokesperson sent an e-mail stating:
"The SPF technical alternative is just now becoming a real focus for the
IETF. It is premature for the standards participants to disclose any IP
they may own related to SPF. If SPF continues to work its way through the
process, there will likely be a point where Microsoft and others will [be]
asked to identify any essential IP claims and Microsoft will follow the
IETF guidelines for disclosure at that time"