Domains are easy.  Domains are hard.  

If you have an established business, then it is a matter of making your domain reflect your business.  You have already established your business identity.  You are good to go

If you are creating a business ground up the most important aspect?  What are you going to call it?  The first introduction to your business is the name.  

Names can make and break your business.  Too short, they don't know what the name means.  Too long, they don't want to type it out.

Read on for more info