Here are some ways to see the signs of an imminent fraud:

1. Free shipping offered.
Item weight would warrant a tangible cost. It is unlikely a true seller would want to give free shipping for no good reasons. Besides if the seller factored the shipping costs onto the item price, then they will lose money and inflating the price of their product - which does not benefit their sales either. Thus, treat this with suspicions.

2. Item price is considerably lower than expected.
Example: If you would know the usual price for a Canon EOS 400D Camera to be about $1000, and the seller is selling at a mere $200, then it's pretty suspicious. That's over $800 off actual price. So even in a discount situation, it is unlikely an item could be lowered so much till it is almost impossible for the seller to make a profit - or even the manufacturer/distributor/producer to cover some reasonable cost. A good gauge is perhaps 20% - 50% off standard retail. Anything over 80 or 90% seems impossible if it's stated as new and unused.

3. Seller's description does not match.
Or has alot of errors - grammatical errors, or on the other end, too perfect. If the description is so picture perfect, then ask why the seller is putting something on auction.

4. Follow up with some quick research.
Easy steps to perform. View the other items on sale. View the past feedback received by the seller by looking into the seller's Rating Points. A high total eBay feedback point does not mean the seller is 100% reliable. It at least means the seller has been selling a lot of products for some time. But look closely into what the seller's history. What was sold, the price of the item. There was once a popular trend to "boost points" by selling 1 cent recipes by email.  Obviously the recipe for a banana cake could be copied from anywhere, and the "cheap" 1 cent price warrants a nice courtesy positive feedback. This way of "farming for points" is not allowed in eBay but has happened before.

5. Extra follow up: Write a quick message to 2-3 of the seller's previous buyers. You could see this from the seller's Feedback Page. And then clicking on the points (number) of each respective buyer (just beside the buyer's Ebay Username shows their eBay Rating. So clicking that will bring you to the said buyer's page. From there, you could do a Message to the buyer to ask for the buyer's previous opinion dealing with the seller. Some buyers may not want to reply, but usually if there was a problematic transaction, chances are the buyer will inform you.

6. Take internet shopping together with its risk in sight. The pros and cons.
Five years ago, there was a reputable laptop computer seller in New York, who sold brand name notebooks, laptops in Ebay. He chalked up over 1000 Ratings, and always delivered on time. Very reputable. Never had a negative feedback. But an individual's personal life, we would never know. So one day, this seller decided to "NOT TO SEND" out the goods anymore. This may stem from the fact that a $2000 laptop, with a 5% profit margin is just $100 profit. And perhaps greed overtook him or some personal problems - whatever it was - when a person has received say 200 orders per week for a average of $2000 per item, that is over $400 000 per week (revenue NOT profit).  And if greed overcame that seller, he might as well ran off with that amount.

In short, sudden-fraud could happen even in normal brick and mortar shops. So always be prepared for such situations. There are pros of buying online. And the cons too. Weigh them sensibly. Likewise, be a nice professional buyer. Be courteous and patient - since buying online is not buying from retail - thus there is a lead time for the goods to be delivered to our door steps.