Hosts file never worked this end... have actually wondered if this is an old XP trick that has been passed on by. Tried using to block Facebook on my laptop (my wife can use it her system - I've locked that down so minimal risk - but like hell is she running on my notebook!!), so found a better solution.
Now what I found was an add-on for Firefox - so lock away IE, after installing FF and setting as default browser (a couple of ways to lock away without actually uninstalling - just ask if you need help). Now I came across FilterFox, but latest version, though free, the dev is charging to actually be able to password protect. Thus I acquired V6, patched up for FF3.5, and
uploaded for others to use
Allows both filtering of key-words in any site and web-search, as well as being able to block ANY site or download location... and fully PW protectable, including preventing any means of disabling the extension.
See attachments for example of what now comes up when trying to open Facebook, and trying to adjust settings