Good point.
Just because you use .com doesn't mean you're more credible or trustworthy. But the opposite may be closer to the truth: not using .com (or ccTLD if outside the US) could hurt your credibility.
Even non-domainers understand that if you use a .net it must be because the .com was taken, and you are a latecomer, more than a pioneer in business. There is mental classification instantly taking place in the minds.
.org is a different story.
.biz is even worse, .us is not first choice either.
I'm not saying this is rational, it's just the way it is. Consumers do not expect to see businesses on arbitrary extensions, they expect one in particular, anything else will arouse suspicion unnecessarily.
I have the same reaction when I see a company using a generic domain: either they were early in the game, or they purchased it, which means they take their image seriously.
When the new TLDs were launched, some marketing 'geniuses' wanted to make them more trustworthy than what already exists. So they implemented screening, red tape and restrictions. That didn't work.
At the end of the day extensions like .pro or .jobs or whatever, that involve vetting of the applicants, do not provide any benefits in terms of credibility, simply because the layman is unaware that these TLDs are restricted... they couldn't care less if you had to take the polygraph test to get your domain.
Ten years down the road .info .biz .pro .etc are still not considered worthy extensions. This is the benchmark for the future. The reality is that ordinary users are not eager to see new extensions.
In practice, credibility means being where your competition is - not in the ghetto.
imho...
