If you are starting a business you should be thinking about .com. It's always the first port of call, but the alternatives are now numerous and just as effective.

Especially with New gTLDs coming, I'm starting to think the .com isn't going to matter that much in the future. People will be using .co, .net, .blog, .ninja and who knows what other extensions. The search engines will react to treat them all equally (other than geographic domains) and there will be no shortage of domains for anyone!