In both WarCraft III and StarCraft, there were profiles in Single Player and it holds all of the unlocked levels in that profile and is able to be transferred to another computer. Since Blizzard is trying to make Battle Net 2.0 similar as and to improve on Xbox Live, Steam, Facebook, twitter, Messengers, and so on, offline Xbox 360 players (No, not the Silver Accounts) were still able to earn achievements and they have an option to "Join Xbox Live" (Whether Silver or Gold) while keeping their unlocked achievements. Though I'm not certain if this is the case of "Guest" in StarCraft II since I consider Guest as a single, limited profile, but if offline players are able to create profile, and at any time if they have connected to the internet with a chance to "Join Battle Net" with that profile, then it certainly should not be a problem.
At the Development Panel I saw, they specifically said that anything unlocked offline will not transfer online. The closest thing I can compare it to is Steam, where you log in the moment you start up the game and go from there. There isn't really a "Join Xbox live" option in this case, as the game is basically supposed to be enjoyed online. I have no idea why, but they want Battle.net to be like a gaming Twitter/Facebook social network.
If the Real ID is like Steam/Messenger, where you have an account name that is likely anonymous to the public while using and able to change their nickname at anytime (Though this too is flawed if used to grief other players anonymously/impersonating [such as the author of the map]), then that's better than having players smurf.
If Real ID uses a method of Diablo II, a main account having a set of individual characters (Aka profiles with their own set of stats, items and name), then that's good too.
The Real ID is basically your e-mail address. I believe you can set your name to whatever you want, but your friends (people with your Real ID on friends lists) can change your nickname as well so they can easily recognize you. Like Facebook or MySpace, the new friends list is an "add friend" system where you have to accept or decline friend invites. This obviously means you can no longer add anyone to a friends list without them knowing.
The example they gave is essentially a scene involving one friend playing WoW and one playing StarCraft 2. With the Real ID system, the friend on StarCraft 2 can message the friend on WoW (regardless of what character or server that friend is on) and they can chat in-game. The same goes for Diablo 3. Essentially it is like Diablo 3 in that characters are bound to an account.
Since (I heard) that Battle Net 2.0 does not record losses, I assume not only it improves moral of playing melee again and again than stop playing, it would actually stop players smurfing to "keep" their main accounts with high statistics, away from losses.
Yeah, basically they set up different ranks of players based on melee skill. If you're the lowest level, you should only be put against players in that same rank. A cool new feature is that it also records pairings, so if you play in a 2v2 with a friend and you guys kick ass together, your team rank could go up separate from your individual ranks. If you play another 2v2 with a different friend, that team's rank is also different from your individual rank and the previous team.
Currently Working On: My Overwatch addiction.