There is still a large part of the population that does not realize how much money can be saved with a few cans of spray foam and a few tubes of caulk. A dozen unsealed recessed lights even insulation contact models leak a bunch of air, on mine it was 5-7 cfm each. Cheap bathroom fans with baffles that don't close can leak a bunch of air. Ductwork that isn't sealed with brush on mastic do or will eventually leak like crazy.

There was some really shoddy work done during the last building boom and tens of thousands of homes leak air like they have a window open, or in some cases two open.

My house was built in 2006 and was scanned with a thermal imaging camera a year ago and all of the vents and registers along with recessed lights and bathroom fans checked with a CFM hood. The results were sickening. When you spend hours sealing things that would have taken minutes to do while the house was being built it really becomes disturbing. The upside is the more I do the more my electric bill drops and best of all the more comfortable the house is.

There is some buzz going on about a 'cash for caulkers' program that would make this an even busier topic.