Then again there is a limitation of the number of characters that you can use in your unique email ID. Getting that unique ID of your choice is also a problem with the service providers. You can go for hosted email by booking a domain name of your choice, but that involves recurring cost. The single sign-on ideas have not evolved to an extent that would allow you to have a unique ID across for all your logins.
I think that we have not evolved much so far as basic thing like an email is concerned. People should have enough flexibility to have a unique ID of their choice. Moreover, we can have them use their own personal email IDs for work by coming up with some technology like adding some headers that will identify their work emails while their IDs remain the same.
Most of the new providers that come up with an email service provide the same things with slight changes or rearrangements. They come up with a new UI, integrate social apps in the email service, and provide chat. Even the much hyped Gmail does not allow you to add an MS Exchange account unless it has a POP or IMAP access enabled. There is a service like Inbox2 that allows you to do just that, but is has a pretty pathetic social aggregation where all you can do is view things for your social apps.
Things are all around there in bits and pieces, and there is no social and email aggregator worth its salt that will allow you do do much. Looks like they are not that well thought out. People are asking for aggregators as they have multiple accounts to manage, but companies that are coming out with them do not seem to be paying heed to it.
One of the services I like is Alternion, but again they have a weird name, more like a sci-fiction movie than an aggregator. They do not allow you to add MS Exchange accounts, and create an email account from their site, but otherwise they are pretty much there. They are adding features but they are loosing out on the time-to-market factor.
Aggregators are the need of the day, and there has been a plethora of them and most of them have wound up because of lack of features that could meet the user requirements. Either they are too basic, or they have too many features. Most of them seem to fail to identify what the users really need and want. Companies need to do their due diligence and then come up with the right aggregator with the right mix of features. They need to evolve and not leave things in bits and pieces.