tycho: Your BKR for Janus Chess is not unknown - it's 1238. You are, however, no longer listed in the charts. I didn't get the impression that inactivity (or activity) is taken in account when calculating the ratings. Only the fact whether or you you're in the list matters. So, for paying members, one quick draws against someone with a similar rating twice a year is enough to keep you in the charts.

This is unlike say, the rating system on FICS, where they, beside keeping the rating, also keep a stat that measures activity - it's an indication how good established your rating is. The more you play, the less your rating will fluctuate (but the more it can fluctuate the rating of your opponent). If you play less, your rating fluctuates more after a win or loss. So, on FICS, having played 400 games way back means a new win or loss can change your rating a loss (just like you have only played a few games here), much more so than if you have only played 20, but all of the recently. And the same statistic is used to determine whether your rating is established or not. So if you have played 400 games the past month, you can be inactive for a lot longer before your drop of the charts than when you have played 20 games in the past month.

While I prefer to have a system like FICS, I think this new system (dropping of the charts if you haven't finished a game in the past 6 months) is better than the old one.