Forbes is running an article in which it interviews Steve Ballmer. In the interview he refuses to rule out taking legal action against Linux where it infringes Microsoft intellectual property. Since the SCO case began there have been very comprehensive audits of Linux, and no copyright violations were found. However, there may be patents which are infringed.
This is an example of how the patent system, which was originally created to help protect the small inventor, is being used by corporations to prevent those same small inventors from competing with them. Often the threat of patent action is sufficient to deter risk averse organisations from considering open source.
Microsoft has been submitting many patents in New Zealand recently. The Word Processing XML patent is currently being opposed by the NZOSS, while we are also looking at several other patents to determine whether they are valid.