1) Who cares? Emails get hacked all the time and since a lot of people will have used the first part of their email address as their user name/login - mistakenly assuming their login information would be private like most other games/websites - it will make it all the easier. If someone has a user name, then there's a good chance they have your email by simply plopping it down in front of gmail/hotmail.com. Couple that with the fact a lot of people will have used common or Elder Scrolls themed passwords...Easy pickin's.
2) How can you change your user name?
3) What?? Not in any of the games I've played or websites I've belonged to. And how can it be more secure? How can my account be more secure by giving half my login information as opposed to not giving half my login information? That makes no sense.
I do think this puts everyone at an increased risk. I wasn't made aware that my user name was going to be exposed to anyone when I created my account. I assumed, like most other people, that my login information would be private like every other game I've played and every other website I've joined.
Even if there were no security issue, I wasn't aware when I created my user name (which has historically been private in games I've played and websites I belong to) that it would be broadcast in game or made public, as most people weren't. If I had been aware, I would have chosen something different. A lot of people will have used the same type of name they use on many other accounts, not knowing any better. For a lot of people the name they chose was private to them and has been used on other private accounts, or reveals information pertaining to other accounts that they don't want made public.
In a guild with 300-500 people's user names exposed, you could run a handful of common use and elder scrolls themed passwords and probably compromise several with very little effort. Wouldn't be hard to guess email addresses from user names as, again, many people, mistakenly assuming their login information would be private, just used the first half of their email as their user name. I'm sure there are many accounts that can/will be compromised in this manner. And with this information known, unscrupulous hackers won't be able to pass up such easy pickings. What have they got to lose? They'll have login user names, and with that they will easily be able to figure out a lot of email addresses, not to mention all the people that use common/easy passwords. Sure hackers will hack, I get it. But why make it any easier for them by handing them an important piece of the puzzle?