Today's domain boom is being fueled primarily by the advertising dollars spent on traffic provided by domain owners. Show your visitors or customers that you are serious about your online business and, in a few years, the domain will probably appreciate in value even if your business does not take off.
Buy related domain names so your competition can't use them for their benefit and against you. What if they bought the domain names that you are thinking about buying? You may NEVER have the opportunity to own them ever again.
And now the domains that you once liked are now being used to against you. Don't look back someday and regret not buying the domain names you want. Domain names featuring prime keywords are extremely valuable because they provide continuous and recurring high converting traffic for domain owners to sell to Web advertisers.
Show your visitors that you are serious about your content. Build sites on good domain names and be proud of the domain names you own. If you are opening an online business, start with a good domain name.