Someone above has confirmed that the e-mail address is only for the initial setup and is not a feature (or even present) in the UI. I don't have SCII and i'm not on PTR, so I can't confirm or deny that. Supposing it is true, though, are the complaints about privacy still important? The underlying idea behind the system is that you do not give your e-mail address to people you do not trust to begin with. The initial exchange should not worry people, as I'm not giving it to anyone but say my friend since high school, or my wife.

The number one concern seems to be "well what if my friend gets hacked" and/or "but the friend-of-a-friend can see my information". If we take the e-mail isn't displayed once it's used as an initial token then there isn't a big issue. Your friend gets hacked, maybe the hacker asks you what your email is because they forgot it. Perhaps you give it, perhaps you don't. I'm not sure this is a valid vector of attack as having your e-mail address is not really the crucial part of the equation. Having your e-mail address is not really the hard part and it doesn't assist them with actually getting the account password. Hackers have enough accounts through trojans that they don't need to sit around brute-forcing accounts given only the e-mail address.

Some people have expressed concern over others being able to access their real name. For most people, I'm not sure why that's a huge concern. Up above there was a female that was concerned about people knowing that fact, perhaps I'm too optimistic or naive about the WoW population but I for one don't care what gender you are. I haven't really met anyone that DID care what gender I am (I play female characters but I am a guy). I find it difficult to accept that someone is going to trawl the friends lists of everyone in WoW just to find a female, and if they did I can't see that being an awfully large population.

Bottom line, I doubt people can long-term see your email address. If they can, then the worst you're likely in for is a lot of annoying e-mail spam (which I'll agree is an awful outcome). The only real security at this point remains an authenticator, and if you're particularly paranoid then use a different password for WoW than for your email service or anywhere else you use that e-mail address. I see how people could be worried about the EULA violation as giving out account information and that is a valid point. Setting up a nickname is not a terrible idea, but that runs the risk of people making the nickname the same name as their Main which is going to flood people with Battle.net friend requests. In the end, if the e-mail address is used only for the initial exchange of the request and then discarded afterwards it really is the best way to provide a handle that is invariant across games. If you are worried about people knowing your real name, then this feature is NOT for you because it definitely is about setting up communication between PLAYERS and not CHARACTERS.