And how would we define "active?" Posting questions? Answers?
I hate to say it, but the reason I went through a fairly prolonged period of inactivity was because I couldn't beat the fastest guns in the west. This is not a criticism, but I visited the site, browsed the questions, found ones I felt like answering, and saw that three or four others beat me to the punch with well-thought-out, well-organized answers. I had nothing to add, and therefore (following the intent of the site) didn't.
So under this scenario, would a user's rep dip because of that? Or is lurking considered "activity?"
What about posting questions but not answers?
What about commenting?
Not to mention TheTXI's excellent reasoning. :)