I have read several guides on eBay suggesting buyers should not accept second chance offers from sellers on eBay.  Not only are they safe (if you follow a few simple rules) but they benefit both the buyer and the seller. Here's how...

Buyers

Why do sellers use second chance offers? There are 2 ligitiment reasons:

1. The seller has more than one of the item available.
2. The winning bidder did not pay for the item.

Buyers benefit because they get to buy an item they wanted at the highest bid they were willing to pay.  The guidelines you should follow before accepting a second chance offer include:

1. Make sure it was an item you bid on.
2. Check the auction end listing and verify the item was sold to another bidder.
3. Make sure the offer comes through eBay's message system (check your messages).
4. Contact the seller and ask why the item is available - if the winning buyer paid for the item and then returned it - pass on the offer.
5. Make sure the offer to pay is through eBay's regular payment methods - it's best if the item is protected by PayPal's buyer protection plan and you pay using PayPal.

Sellers

Sellers benefit because...

1. They get to sell additional items for eBay's final value fee and not incur additional listing fees
2. They get to sell the original item to the next highest bidder when the original bidder did not pay for the item, without incurring additional eBay listing fees

Sellers should always...

1. Use eBay's standard second chance offer feature
2. Should not offer the item outtside of eBay
3. Use eBay's messaging system to communicate with the buyer

Second chance offers are a win-win experience when everyone plays by the rules.  Buyers get the items they want at a price they are willing to pay. Sellers get to sell their items at the highest possible price with the lowest possible cost of selling.

Good Luck! I hope you enjoy your eBay experiences as much as I do - both buying and selling.