I have a pretty long list of time-wasting sites in the hosts file and it is working just fine, however I'm experiencing a very strange behavior - every day or two (my PC turns on automatically every day) from the file disappear two lines:
127.0.0.1 youtube.com 127.0.0.1 www.youtube.com
Even the line-breaking symbols stay there. I am using the latest stable Chrome and two Youtube-related extensions - FancyTube and YouTube Ratings Preview. I don't remove them because sometimes I need to visit YouTube and I don't want to deal with advertisement or rickrolls. The interesting part is that I tried to make the file read-only and to remove write-rights from everything except me, but it didn't help (flags haven't been reset). Is it one of the extensions or something else? Or maybe Flash?