Buying these on eBay is a great way to save some money on stores that you shop at regularly. They also make a nice present for family and friends if you know they like shopping at that particular store. People sell them because they have redeemed their frequent flyer points for a gift card and would rather have the cash, or they have received them as unwanted gifts or prizes.

Some hints:

• some gift cards / vouchers have expiry dates
• Westfield gift cards are not valid at the big retailers like Woolworths, Coles, Myer, Target, Big W. I have checked with David Jones and they are accepted where there is a David Jones store located within a Westfield centre.
• if the Buy It Now price is too good to be true - it probably is. Unfortunately there are some dishonest and unscrupulous people out there who are scamming the eBay community by offering non-existent gift cards / vouchers
• check the feedback rating of the seller - have they sold gift cards before or do they have a good seller rating? Are they a recent eBay member or have they been a member for a long time? Most long-standing eBay members with good feedback rating are not going to risk losing their good reputation  by trying to scam you
• remember it's not a great bargain if you pay for a cheap gift card but get scammed