I'm more in line with the aggressive approach when it comes to the neighbor list. It has always been this way for me.
The recent introduction of the Friend Point system, though, certainly seems to be helping to motivate others to be a little bit more attentive to who they add/keep as neighbors now.
I'm a daily player, so I aim to have neighbors of a similar playing pattern. Unless they contact me directly about an extended leave or something (or I see a post from them here to their neighbors in general, as one of mine did not too long ago), I will remove them from the list if they've gone 2+ days without any activity.
No mucking about, for this tapper. ;)