Yak Shaving

One of my friends used this term during SDQI presentation and I was interested to know the meaning of it. Here are some meanings obtained from different sources:

1) Any apparently useless activity which, by allowing you to overcome intermediate difficulties, allows you to solve a larger problem.
I was doing a bit of yak shaving this morning, and it looks like it might have paid off. (http://en.wiktionary.org/wiki/yak_shaving)

2) [MIT AI Lab, after 2000: orig. probably from a Ren & Stimpy episode.] Any seemingly pointless activity which is actually necessary to solve a problem which solves a problem which, several levels of recursion later, solves the real problem you're working on. (http://www.ist.rit.edu/~jxs/jargon/html/Y/yak-shaving.html)

3) "Yak shaving" is a programmer's slang term for the distance between a task's start and completion and the tangential tasks between you and the solution. If you ever wanted to mail a letter, but couldn't find a stamp, and had to drive your car to get the stamp, but also needed to refill the tank with gas, which then let you get to the post office where you could buy a stamp to mail your letter—then you've done some yak shaving. (http://en.wiktionary.org/wiki/Citations:yak_shaving#English)