Testing a system that is not only not yours, but where you have not been asked to do such testing is only asking for problems. People are hyper sensitive to this right now and don't like any flaws in their systems being pointed out to them.

It's a very fine line between doing that and accidentally tripping across something, case in point I went to check out a router manufacturers ftp site and saw the .txt file with the YoU arE OwNeD title. I just closed my browser and emailed customer support and left a phone message for them as well alerting them to the issue with my name, company name, time, date and why I was accessing the ftp site. No one ever called me back (didn't expect it) but I still worried (since I'm a bit paranoid ) but as I said above, companies are a bit quick to pull the trigger these days and the penalties are getting larger for "accidentally" uncovering problems.

*edit* Yes, I did open the .txt and it was obviously not supposed to be there