I gave a lot of thought to this topic and almost wrote an article about it myself but I finally concluded that there was pretty much two issues at hand:
1) Chances are, if your gift target is a good candidate for a dedicated reader, they already have one by now or plan to get a specific one. If you're going to gift it to them you need to know that specific one, or you're just going to be giving them something to take back to the store.
2) The bigger issue is that, in a large way, giving a gift of an eBook reader is like giving a gift of a cell phone contract. Though they are less aware of it. In most cases, you're going to be leading them towards tying themselves down to a single store and so on. It's a bigger decision than which device you like, especially for people who don't already know about public domain books, and non-DRM sites, and all that.
So, I figured... either you're giving them shackles or you're giving them what they already have or risking a huge annoyance. Not very good odds on it being a great gift. But if you KNOW they want it, and know which one... go for it
