Not for illegal activity, according to an article on Tech Herald:

"Logs, seized equipment, and testimony from those arrested, seems to be the undoing for those connected to Anonymous and LulzSec. ...According to HideMyAss.com, ...services such as ours do not exist to hide people from illegal activity. We will cooperate with law enforcement agencies if it has become evident that your account has been used for illegal activities

The service stores logs for 30-days when it comes to Website proxy services, and they store the connecting IP address, as well as time stamps for those using the VPN offerings."

Furthermore - if you're using a VPN service to stay anonymous, you're only staying anonymous from whatever you're accessing, not the VPN service itself.

I wouldn't trust this service, because I can't find any information about who is running this service - at least not in the few minutes I have spend clicking around on their site. Maybe there is some info somewhere, I have not found it.

In another comment a quote from a different article was mentioned regarding the Terms of Service. I could not find a page about the terms of service. Maybe it's me, but I think that these informations should be easy to find on a site.

Some other interesting points about this service are explored in an article by rsnake from ha.ckers.org:

http://ha.ckers.org/blog/20100104/anonymous-proxy-woes/

"So yeah, please don’t use CGI proxies, unless you really know what you’re doing. They really very rarely increase your security. Most of the time, they just decrease it, as a matter of fact."

I always thought the main purpose of things like HideMyAss.com are to get around stupid filters installed at your workplace or school. Thankfully neither for me have filters, but I've visited my old high school a number of times and I just throw everything through an ssh connection to my home machine.