I'm often asked why there is wide fluctuations in FeedBurner feed stats, as shown in my and other FeedBurner chicklets. This fluctuation can be as big as 10-20% of your total subscribers. The fluctuation is caused by the way that FeedBurner counts subscribers. For most native RSS readers, FeedBurner counts every unique IP/User-Agent as a subscriber. Since people turn off their work computers on the weekend, there's usually a big dip in subscribers on Saturday. As people return to work and startup their native RSS readers, the subscriber count increases all week. Here's my FeedBurner stats graph for the last month, which confirms the trend.
Thanks for the information Randy!
I always get discouraged on weekends and this helps explain why my readers all drop me then rejoin me the following week. :)