I think both will remain in 2010, yeah effect will be less then 2009 , as they have to face tough competition site like ezdia which is growing up at a good rate will give a good fight to these sites and may be sept of 2010 it will become more effective then these So lets see what is going to happen but a great year in social media is coming ahead and will reach to great height
As long as they both continue to evolve and provide a service to their audience, there is no reason why they can't carry on.
Another related question - is there anything like Twitter or Facebook that is going to rise in 2010? What is this year's social / network / fad?
Social networking is still in its infancy as far as I'm concerned. In one form or another facebook & twitter are here to stay. I agree that the younger generation is likely to attach to their own network to avoid having to deal with sharing space with parents and bosses.
Absolutely! I tink that Facebook and Twitter rock. I love them a lot. A lot can be done with those two sites. These two sites are grea for marketing.