Are you in the market for a new printer? If you have more than one computer, chances are you'll want a network printer rather than a simple USB printer. A network printer can be placed in a central location, and isn't tied to one particular computer.
The printer market seems to be improving now, but a year ago you would face an odd dilemma: many network printers lacked wired ethernet ports. They were mostly Wi-Fi only! What's the advantage of wireless over wired in a printer? A printer isn't something you carry with you from room to room. A printer needs to be plugged in to a power outlet, as well as a phone line if it has a fax capability, which means you'll keep it in a fixed location, such as a study; right where you have your broadband router.
There is one situation where Wi-Fi might be a useful feature in a printer: if your home/building isn't wired for ethernet, and you wish to place your printer in a different room to where you have your router. But most people do have their routers in a central enough location, and people aren't exactly un-used to having their printer placement limited by a 1.6m USB cable anyway, so this is hardly the norm.
On the other hand, there are significant disadvantages to relying on Wi-Fi for your printer. It makes the printer more expensive. It's more fiddly to set up than simply plugging a printer into a network with a physical cable. And, in the middle of a tricky situation, you may find that your printer's wireless connection is less than dependable. For most people, a Wi-Fi connection for a printer will turn out to be more a burden than a blessing.
Perhaps this is an instance of marketing gimmicks over practicality. 'Wi-Fi' sound like advanced cutting-edge technology, and rolls of a salesman's tongue a lot more smoothly than 'wired ethernet,' which, while fast and dependable, has already been around for decades.
