Social networking is Time Consuming

My marketing plan includes spending about an hour a day on the various social network sites associated with opportunities to market my book. For me these include LinkedIn, Plaxo, Facebook and Twitter. Today I have spent three hours just working through a subset of these. Perhaps my plan is going to take more time than I had expected. On top of that I can't figure out how to use Twitter. So far it's useless but I'll keep trying. I do notice that a number of people tweet for awhile and then seem to give it up. So maybe I am not the only one that it doesn't work for.