How necessary is that? Does it depend on the eReader? I use a Sony 300 series (which I personally think is about the high point of the eReader evolution, with the exception of the 350 for more screen space in an almost identical sized casing) which is as thankfully dumb and disconnected as eReaders get. It plugs in like an external hard drive and I simply copy epub files onto it.
You couldn't pay me to have a kindle (well, you could, but you'd have to pay me a lot and I'd just sell it and get another Sony).