I know a fair few folks use Hola to bypass government site blocks, I've used it myself on the odd occasion. Folks also use it to watch BBC iPlayer etc from outside the UK.
Unfortunately the owners of Hola have been a bit sneaky and have been selling off (your!) bandwidth to anyone who can pay - Hola is a peer to peer network, similar principle to torrents and rather than going into a long rambling technical explanation of how they manage it all I'll say is avoid (uninstall) Hola for the time being.
In addition, at least two major vulnerabilities have been uncovered both of which could potentially allow your computer (and internet connection) security to be compromised.
A more worrying aspect is that when someone pays for access (to your bandwidth), anything they do while connected via your computer appears to come from
YOUR Ip address. Now... just think about the implications there.
This article probably describes the main issues a little bit better than I have.
UPDATE: Hola is definitely dead as far as casual users are concerned.
Vectra Networks have analysed it and found that malicious users can download software to other Hola users machines.
JF