If you don't want an existing snipe placed, a short term solution is to change your ebay password. That will block AS placing it.
I wouldn't worry about snipes getting placed. The only time snipes didn't go thru, that I can remember, was due to that time internet was experiencing "The Worm".
When there's a problem, it seems to only impact adding, deleting or changing a snipe.







(Hopefully this will avoid reduntant posting.)