Twitter's model
Twitter seems to be proud of the fact that it has no profit model. I'm imagining that the company will want to keep the hype building long enough to sell the company for a few billion dollars. This is great for Twitter, but when the platform becomes obsolete and goes the way of Friendster, the marketing folks that are evangelizing Twitter now had better have an alternative.

I also cannot foresee Twitter's user base growing too much higher than it is now. The limited and obscure nomenclature (RT, @username, #, etc.) will confuse the masses. The simple functionality of Twitter will also lead to a glut of competition in the next few months, with companies duking it out for the best implementation of the microblogging model. There's not enough to Twitter to keep it on the top of the heap. Being first in this case, as we've seen, is not a guarantee that you will have longevity.

Google Wave
Just in the time that it has taken to scope out this article, Google announced its next big initiative: Google Wave. Wave is an open source initiative that promises to overtake both email and social networking. I would encourage anyone interested to view the demo. 

Wave seems to be another paradigm shift in terms of online communication. Emails, tweets, and communication within social networking sites could all quickly be replaced by what Google is calling "waves." This is the type of innovation that will fold all communications into an easier-to-manage package. As much as I enjoy my time online, I do not enjoy logging into five different sites and an email client to manage my communications.