[CrazyStat]

> You need to defend your trademarks otherwise courts will render them moot.

Sort of.

You need to prevent your trademark from becoming generic.

You also need to go after infringers in a reasonable amount of time, or you may lose the ability to collect monetary damages from that particular infringer at a later time (laches); however, progressive encroachment mitigates this to some extent (if you ignore a minor infringement, you can still sue if the infringement substantially expands, overriding the laches defense).

There's no requirement that you defend every case of trademark infringement, that's just overzealous lawyers who like to get paid a lot of money for sending threatening letters.

In this case Bose could ignore Boze and it wouldn't cause any issues. If Boze later expanded their business in a way that would increase the threat to the Bose trademark (for example, launching their own branded headphones, or directly competing with a Boze iOS app) then Bose could sue at that time under the progressive encroachment doctrine.

All that said,

> In this case it would be completely normal and legitimate for Bose to sue.

is completely correct.