The premise of eBay is a simple one: members list items for sale, and other members find those items and bid on or buy them. It goes without saying, of course, that when prospective buyers search eBay with the intent to buy, the only find those things that match their searches. It also goes without saying that as a seller, the best way to get more bids is to have your listing seen by more buyers.
This conspiracy of facts often leads sellers to engage in what is commonly known as keyword spamming, a seemingly innocuous practice by which sellers list their items with additional, often unrelated words in them with the intent of causing their items to appear in broader variety of buyer searches.
For example, a seller with a pair of headphones or earbuds to sell would be keyword spamming if their auction description read:
"New Sony headphones for your iPod phone camera laptop TV!"
Now this description is not inaccurate per se—it's true that a brand new pair of Sony headphones might be usable on all of the listed devices. The problem is that what's for sale here is not any of those devices, and yet it will appear whenever other members want to buy an iPod, a phone, a camera, a laptop... you get the idea.
While as a seller it's understandable that you want as many buyers as possible to see your auctions, as a buyer you've no doubt had the experience of trying to search for an item on eBay only to encounter thousands of unrelated results that are time-consuming and annoying to filter through.
Keyword spamming ultimately doesn't help sellers much—most of the time, buyers are looking for something specific, and if your auction isn't that item, they're not going to buy. At the same time, it hurts everyone on eBay by making buying more difficult. Keyword spammers hurt other sellers, toothe headphones seller who lists 400 sets of headphones for sale with the word "iPod" in the title is making it harder for the iPod seller to sell his or her wares, since buyers will have to filter through hundreds of "headphones" auctions in order to spot the odd iPod for sale, or use advanced searching techniques to get what they want.
What To Do InsteadIn a word, don't do it. Limit your listing's title in particular to the name of your item and particularly relevant properties of your item—for example, terms like "new," "in box," "used," "size 8," "blue," "worn," "vintage," or other adjectives or properties that actually relate directly to the item you're selling,
If you feel that you must list the 101 things that your item can be used for or with, or what sorts of items buyers who bought this item are also likely to buy in addition, do so in your item description where it's still informative but is less likely to foil buyers' search attempts.
As a final note, beware that egregious keyword spamming is at times also dealt with administratively by eBay—post 100 listings with bad search terms in their title and they could all disappear with the first buyer complaint. That doesn't help sales, either!