Since this thread is presumably being read by entrepreneurs making bets on the future of technology, it needs to be said that this will never happen with the current imaging technology. Brainwaves implies EEG, and the research in this field strongly suggests that it is information theoretically impossible to extract this information through the electrical activity on the scalp.
For this vision to become reality we need a new imaging device that has both the temporal resolution of an EEG, and a spatial resolution that probably needs to be better than an MRI.
In summary: Certain things are impossible. I can say with certainty that no algorithmic improvement will allow this to work using an EEG. I don't know whether it is physically possible to create a non invasive imaging device that allows such a signal to be detected reliably, but it certainly does not exist today, and it seems like a leap of faith to assume that it definitely will exist at some point in the future.
I've invested an extraordinary amount of effort into improving the speed at which I can interface with a computer; I think the practical limit is about 300 baud, half-duplex.
Of course, we're trying to establish an interface with a bafflingly complex lump of grey meat, but are we really daunted by the idea of outpacing a V.21 modem?
What about the inverse, that the humans learn how to think in a way that a computer understands? That will be much easier, as humans learn much better than computers, and also much safer - I will have complete control over which of my thoughts the computer can detect and interpret.
It is possible today to make EEG controlled devices. They typically differentiate between a small number of real or imagined movements in the user. This is awesome, because it can allow severely paralyzed people to communicate, control a wheelchair. etc. Nevertheless, the algorithms used to do this are perfectly useless when it comes to distinguishing whatever words the user is internally vocalizing.
Edit It seems that more direct methods of neural interface are already plausible: http://www.technologyreview.com/biomedicine/37873/
Wikipedia has undoubtedly changed how our generation views knowledge, but it's still a pull-technology. Outbound messaging will still be a push-technology (nobody wants to compose an email of their stream-of-consciousness, and brains are poorly wired to retain full structure in mental 'RAM')
Wetware doesn't add significant differences to the existing protocols - merely a more rapid input mechanism than checking your phone. Assuming contact is voluntary, people will not opt for the PubSub model for comms. If you choose to use it for trivia, caveat emptor.
It will be very interesting to say the least.
Personally, I am already overly unacceptable to the karma endorphin boost from reddit, quora and HN. I was thinking about this just the other day; I was originally against karma being hidden on posts, but now, I like the fact I am less enticed to for bias based on that number.
We already continually scan for karma upticks on all our primary sites. This is bad...
We will wear a device which will be able to read our brainwaves and determine which word we are thinking ala dictation, then send that to the recipient.
This will be wired-telepathy - the recipient will get a message which they can receive any way they choose; visually (email - they read it) audio playback, or thought-injection. It is played back on the nerves and is "heard" in their head as a thought. (evolutionary results to be sure)
As a life long Cyberpunk enthusiast who, at 37 years old, has been using computers daily since I was 8, I really have concern over the mental health of the yet-to-be digital world.
I.E. the ADHD that will result in direct cerebral access to information 24/7.
What will be the impact on the (generally) serially wired brain to vastly parallel inputs?
I suspect massive upheaval on the social level. There will always be adopters of immersion, as there will be the future Amish who will eschew all digital, but the median social reaction will be a result more of our true, and unknown, innate biology that we wont even be aware of until this happens.