Why does it matter? There are so many available TLDs now that it shouldn't really matter which one you choose. Too many people seem to think that .org can only be used by non-profit organizations - which is simply not true.
According to what? There is no restriction when you register a domain. org is short for organization, just like com is short for company. I see lots of .com websites owned by individuals or non-companies. It is definitely a guideline and not a hard-fast rule. The only TLDs that are actually enforced are ones like .gov and .edu.