I only open the Bitcoin-QT once a day to download blocks and then I immediately close it.
Me too. Plus, I also do this...
I guess many people are running the bitcoin client through Tor, those don't show up.
... since I found out some people are trying to link your IP to all your transactions.
Actually, I really think that putting bitcoin behind Tor should be a "recommended practice" as using different addresses for each transaction, and that allowing the bitcoin protocol to exchange, recognize and publish hidden services should be a development of high priority.
People should not be exposing all their transaction history so easily...