First off: Don't buy anything off of eBay, Amazon, craigslist, or any other auction/trade website without actually researching the product, and what it mostly sells for. Some eBay/craigslist vendors say something is a popular device and sell it at a very low price. In reality, these phones are basically Chinese, Vietnamese, Korean, or Taiwan knock-offs. These counterfeit devices are slow, buggy, poorly built, and also very, very frustrating. DON'T get electronics that have a stock picture with a very low price. Many of these can be fakes, as most people assume that the product is real and not a knock-off, so they will buy the item. This is a ploy from manufacturers to get you to buy counterfeit items from them. DO question the seller on the item. If the seller is answering questions in a vague sort of way, or not answering at all, then the seller may be fake. DO look at the description. Sometimes it may tell you that the phone is counterfeit. If the description lists features that the original phone doesn't have stock, then the phone may also be counterfeit. DO research what copies of the device are out there.
I can make it a lot easier for you: just look at how much the original (branded) product is worth, and how much the one you're trying to buy is worth. Sure, you could be trying to save, but if something is way cheaper than the branded one, then it's definitely a knockoff.
Good advice. It's always best to do your research first and read the small print. Especially when buying from amazon or ebay. If in doubt then don't purchase it and get your goods from a more reputable source.
That's why I don't really buy gadgets online as much as possible, because it's very easy to get scammed. I only buy gadgets online if the seller has 100% positive feedback and after researching on the reputation of the seller. I also think that it's much safer if you buy gadgets or any electronic item personally, in a large reputable store or mall.
Fake electronic devices are easy to spot. Why? Because they look cheap as compared to original electronic products. Before actually purchasing a product, try it out first. If the interface looks pretty darn bad and also very clunky, it's a fake. Take a look at the manual of the device. If it's written in poor English, it's fake.
Plus you should always remember to research the buyer before buying anything. A lot of sellers sell fake goods even on reputed ecommerce sites so read the reviews about the buyer before you decide to order something. Remember if there is a big price difference between what you expect and what you see on the order page, there could be a problem. Not everything that is available for less is a genuine product and you should try to find out why it is available for so less.
If the price is too good to be true, then most of the time it's a fake. I agree with the chinese knockoffs. Don't fall for their free shipping deals. Stick to buying from major retailers or buying in store when you need to buy a big ticket item.
I greed about the price, anything that's too cheap will end up becoming expensive on the buyer, either with repair costs or cause he'll need to buy a new one. However there are a few good Chinese electronics, some of the tablets, while being cheap, are pretty good.
One thing to keep in mind regarding price, sometimes a seller on Amazon will purposefully start off selling their items at a lower price to get more people to attract more people to their listings right off the bat, then they will gradually increase the price of the item over time. I'm not a seller on Amazon, this is just heresay about how some of the sellers try to achieve higher listings on there - nothing really shady per se, they're just selling their items at a discount in the beginning to gain some popularity with their listings vs. others. They usually make it up with high shipping though too. Amazon also has a program whereby they will house all of the sellers merchandise and handle all the shipping for them. This is usually labeled on the listing itself that the order will be fulfilled by Amazon. This might be a little bit safer too, though I've heard of counterfeit items slipping through this process as well - in one case it was memory cards.
Also if a cellphone or smartphone model that has long been discontinued by the manufacturer is readily available in brand new condition from a seller on Ebay that has lots of them in stock, then you can be sure that it's fake too. They may look original, (the operating system is also original because they just downloaded it online) but they are not the genuine ones.