If you lose, you know it's because someone was willing to pay more. But, remember, if the high bidder later retracts his bid, you may become the high bidder and be obligated to purchase the item. If you've been outbid with plenty of time remaining in the auction, and have located another item you would like to bid on, contact the seller and ask permission to withdraw your bid. This will be a bid that is high enough to make you the high bidder for the time being. You can check in from time to time to see how your bid is holding up, and if you are outbid, you can place another bid at a later time.
Some bidders consider sniping unethical, others swear by it.
The fact is, it is perfectly acceptable on all auction sites. Locate an item you would like to purchase. You may want to open a special folder for these bookmark auctions. Carefully note the day and time that the auction ends. Be at your computer at least 3 minutes before the auction ending time.