As I mentioned the other day, many media outlets have been reporting incorrectly that Tim Tebow had been granted a trademark on the act of "Tebowing," not just the term. To some extent this may have been a misunderstanding of an original Associated Press report in which the AP might have been joking (which goes to show that it's best if people can tell when you're joking and when you're not). In any event, it was wrong—he trademarked the word "Tebowing" and is not seeking to preclude others from actually Tebowing, should they choose to do so.
Meghan Lalonde provides some more detail in this post at Legal as She Is Spoke, which is a project of the Law and Journalism Program of New York Law School. "Kudos to Lowering the Bar for getting the law right" on this, she writes, and I hope that sufficiently shames other media outlets into doing their homework next time. I mean, I'm not an IP lawyer and I stay drunk most of the time, and even I was suspicious of the claim that somebody had trademarked a pose.
Lalonde points out that the Lanham Act defines trademarks as "words, phrases, logos and symbols" used in commerce, and so although an image of a man Tebowing would probably qualify if used to identify goods or services, a physical pose would not. Seems like there would be lots of other practical problems with enforcing a trademark like that anyway, such as if the alleged infringer just stopped doing it whenever you tried to get a picture as evidence. "I'm Tebowing … I'm not Tebowing. I'm Tebowing again! Now I'm not." Irritating.
On the other hand, she also says that according to Marty Schwimmer, who writes The Trademark Blog, a "trademark for a physical motion" is possible under the Madrid Agreement, which is something having to do with international registration of trademarks that I was planning to summarize for you but I suddenly got very sleepy while reading about it. Suffice to say, if you have a physical motion you'd like to trademark—and who doesn't—it might be possible to do that under this Madrid Thing. Please consult an expert before attempting to trademark any physical motion, especially one that is dangerous in any way.
In any event, there is currently no trademark (or patent, or copyright) on the act of Tebowing, so please continue to Tebow if you so desire.