Remember, though, that in many places ignoring something can put you at risk for a default judgement at a later date. It'd be nice if we could just ignore troll trash :/

Ignoring a court summons or lawsuit or something, sure, that's risky, don't do that. Last thing you want is a default judgement.

A C&D letter? Nah, you're 100% safe (legally) to throw that in the garbage.

The main potential legal impact of a C&D letter is that, to the extent that notice is relevant to the existence or degree of liability, itay give you enhanced liability after the letter than what you had before. Other than that, yeah, its just basically a formally-written “please stop” letter.

Of course, there's always a possibility that the party sending it follows through on the at-least-implicit threat of litigation.