I've completed German Basics 1, Lesson 1 a few times with no mistakes, but Basics 1, Lesson 2 is still locked and it says that I have 0 words learned. It could be a problem with my computer, but everything seems good with cookies, Flash (microphone), etc. I also tried the first French lesson and got the same result.
What does "over aggressive" mean? My internet has no issues caching responses from any other website on the internet. This just sounds like lazy coding to me. Why bother fixing a server issue that only affects a small number of potential users, right?
Most websites have relatively little in the way of interactivity. DuoLingo has desktop application-esque functionality. Heavy caching will therefore have a greater effect on it (as I understand it)