>>> You can't prohibit it, since you are not allowed to monitor it's usage. Yes you can! It's very common for companies to block access to gmail.com facebook.c

>>> You can't prohibit it, since you are not allowed to monitor it's usage. Yes you can! It's very common for companies to block access to gmail.com facebook.com and similar websites. I am not a laywer but that's a clear message that's it's not allowed. Circumventing with proxies/VPN should be grounded enough for termination.