Trademark owners have to defend their trademarks, or risk losing them.
Should have worded it better. That's what I meant. I don't know how relevant it is. Suppose Oatmeal Studios sue some fictional "Oatmeal Cards" and "Oatmeal Cards" argue that they didn't defend their trademark as they didn't go after The Oatmeal. Can't Oatmeal Studios claim they weren't aware about The Oatmeal's existence?
There should also be a specific trademark search available, not sure what that would be in the US.
Did Oatmeal studios contact Innman first before bring the suit?
What I was saying was TheOatmeal started as random comic. He might have checked for existence of a similar entity at that time. Most likely, he assumed getting a domain name means no one with the same name exists. Merchandise was gradual expansion.