Despite popular belief, eBay sniping does not violate any rules. An eBay representative acknowledged that "sniping is part of the auction process".
eBay could put a system in place to end sniping very easily if they wanted to.
Think about it - you're placing a bid like anyone else, you're just waiting for the last few seconds of the option to do so.
How is that unethical?
I consider that simply "being smart".