browser cache: movies don't get prefetched and do not stay cached anymore

[clueless]

This is not strictly about stream-downloading. A year ago I was able to watch movies in my browser, then dig up the flvs in my browser cache. All I had to do was to merge and rename the files that just sat in a hidden directory. Apparently since then all browsers got their caching mechanism redesigned.

I use Safari which has introduced a single-file sqlite database, and while I can dig into it I can not find the flvs as I used to be able to. Experimenting with Youtube, I also find that Safari does not preload the whole movie as it used to. Does anybody know what is happening now? It seems to me that movies don't get prefetched and do not stay cached anymore. Is this really what is happening?