Originally Posted by Ortep
I personally see no use for it. It will be a heavy drain on the battery compared to the unit itself. So you will want to switch it off during normal use. And if you have to switch it on for the transfer of a book (once a week max) it will be faster to plug in the USB cable. You will have to do that anyway to recharge the unit. So for me wifi is only extra work, extra money end extra short battery life
That might be true for a specific implementation but you can implement support for WiFi always being on and still have good battery times as seen in the Nokia internet tablets.