It is false, Zed. This revolves around the idea that someone who infringes on your IP might be able to go to court and say that they did so in good faith, on the basis that they understood tha tyou had allowed previous infringements to stand.

This is a legit worry, but it's not the same thing as "if you don't defend your IP, you lose it."

There are different kinds of infringement. If a nonprofit daycare center paints your registered trademark characters on their walls and you let it stand, that means that other nonprofit daycares can probably defend subsequent uses of those marks.

However, it DOES NOT mean that your commercial competitor can use those marks on, say, their rival themepark. Judges aren't idiots -- it's not credible that someone from, say, Universal Studios who showed up in court to defen thteir new "Mickey Mouse Action Adventure" ride on the grounds that Disney, say, had allowed their marks to be used by a daycare would be acquitted.

There's this idea that IP is like virginity, off or on. In fact, it's a continuum, and failure to defend does not engender loss of all rights.