If it spells something, sure. But with .biz being so popular, .bz is the redheaded stepchild. Something that could come to fruition ONE DAY is that .bz as a typo for .biz pop sites.
If you are really keen, try those 2 letter .bz domains that are available for sale at $xx at places such as Afternic Bazaar
I got one .bz site at http://lao.bz .. so far, not so bad I think you should develop the site further if you want to make $$ from such .bz site. The domain alone..hmm.. may not be that popular.
There is a common thinking that .com domains are good and the other domains are being rubbish. It is a pity that many "learned" views had been given by those who had not being using the other domains. I'm no expert but I have a variety of domains, .com, .net, .info, .ws, .com.my, .net.my, .cn, .hk.cn, .tw, etc. I have no problem with the search engines.
Search Engines are fine, but if you're seeking to develop a BRAND or to resell the domain name to an end user, not an SEO-phile who can make any domain (Including crap random letter/number domains) rank high, why go for the Holiday Inn when you can shoot for Intercontinental?