Yes, short matters. If you can say the same thing, with fewer syllables / less letters, while keeping 2 - 5 in check, it's a no brainer.
Of course, if you can support your long domain, such as "ISoldMyHouse.com" with hundreds of weekly radio placements featureing a "catchy" tune, you can probably drive home a longer name too.
There are no hard and fast rules, but the guidelines that I mentioned above are tried and true.
1. Is it short?
2. a. Is it easy to spell / misspell?
2. b. Can a person tell a friend about it and is there a chance the friend will actually be able to just type it in?
3. Is the .com version available? If not, are you trying to do the delicious thing?
4. Is it really witty, or have you just convinced yourself that it is cause it's all you could find?
5. If you're going for the straighforward thing, is it really straight forward? Or again, have you just convinced yourself it is.
Good luck.