[lutusp]

> Not a lawyer, but as I understand it, trademarks often cover only specific market categories. That is, someone can in some cases use a trademark in a market category that the original trademark owner does not operate (e.g. Company1 using BrandA sells only consumer electronics, some Company2 can actually later use BrandA to sell baby diapers). As long as BrandA isn't sufficiently famous and there is no risk of confusion or brand dilution, then Company2 isn't necessarily going to get in trouble.

This is true, and when a trademark holder attempts a legal action, they have to show a possibility for public confusion and loss of business to the "infringer". This is why Apple Music (the Beatles) and Apple Computer were free to coexist for decades -- no prospect for public confusion.

By contrast, there's a now-famous case in which someone whose name was McDonald, and who operated a restaurant named "McDonald's", was obliged to rename his establishment after the other, much bigger McDonald's brought legal action on the ground of public confusion. The fact that the man's name was McDonald wasn't sufficient grounds to justify the name.

I had a legal tangle which this protected-word issue. I once had a Web page that provided sunrise and sunset times. I foolishly called it "Sun computer". The other Sun Computer quickly threatened legal action for my use of the protected word "sun". No, boys and girls, I'm not making this up:

http://www.arachnoid.com/lutusp/sunrise/#The__Sun_Computer__...