Hah. Last year I've significantly cut down the number of "friends" on facebook. 6 months later, one of them was the first to notice this missing connection. When asked why, the response was essentially "_because_ it took 6 months to notice" (on top of the original criteria for 12+ months of no communication via FB).

So in the alert message, can you include "... but it was N months since you've last talked, so whatever."?