You should probably ask a lawyer, but as I understand as a layman if it can be demonstrated that you knew about an infringing trademark but ignored it, it is a

You should probably ask a lawyer, but as I understand as a layman if it can be demonstrated that you knew about an infringing trademark but ignored it, it is a lot harder to win a lawsuit. I think the basic idea is that trademark rights are valid for as long as you need them, however you lose those rights if you abandon the mark. I think that ignoring infringement is a piece of evidence that the mark is not useful for you anymore. It may not be absolutely critical, but certainly doesn't help. Suppose some other company markets the brand "The Fourth Ace" using the South Butt logo, and they get successful and start stealing business. The North Face sues them, but have trouble in the case because North Place points out that their logo is a variation on South Butt, which doesn't seem to bother them.