A DUNS# should be taken seriously, it can help make you or break you. You can usually set up a company profile for free. But to build a credit profile it does cost some money. A credit profile can be beneficial to get you started, because you can pretty much pick which creditors you want on that profile.
Once that number starts getting around, companies can report good/bad business relationships, debt repayment history, etc.
It's a double edged sword that you should really be careful with.