Do4600 said:
I had absolutely no idea trademark law was so convoluted.
With the caveat that I'm not a lawyer, and I never studied trademark law while I was in school... the undergrad law classes I took were enough to scare me off law school...
The basic idea behind trademark law is to protect an individual's identity in the market. You trademark your company's logo so someone else can't use it, you trademark your products so no one else can turn out cheap knockoffs of your product.
With copyrights (which I did study formally), when a company goes under, those properties are almost always sold off as part of the bankruptcy. If there's a TV series or comic book you loved from a company that went out of business, it's a pretty safe bet that
someone bought the rights to it at some point.
For instance: the rights to everything CrossGen comics published ended up with Disney after CrossGen went out of business. Disney had nothing to do with it, but they picked up the rights on the off chance they'd be useful later.
While I'm not sure if this can happen with trademarks, the law appears to suggest that it shouldn't be expected to. If you want to name your product something, and that matches someone else's product from 10 years ago, it's on them to let you know they exist, and that they still hold the rights.
The concept seems to be that if the other business folded, there would be no reason for them to care about you registering their trademarks, and it would be an unreasonable burden to ask every business to go through the entire archive of trademarks whenever they wanted to fire up something new.
I'm not sure if this helps clarify or only makes things more confusing, but I hope it's the former. Anyway, sorry if this is more information than you care about.