Any experts using social networking sites such as myspace, facebook to market products efficiently?

Community Sites are great Sites you can post articles and put Sign on articles like me

We use a lot of community sites like facebook and myspace for our advertisers, and depending on what your product or service it can have one of the highest ROI!

Which one do you consider better: Facebook or MySpace?

depends on your goal... but typically myspace is better in terms of price and performance. i would even suggest if your product or service relates to a specific vertical, you target a group of sites. limiting yourself to one site is a bad idea, even being a profesional, every campaign can bring new and interesting results.

Community sites are a great platform to develop our business better. Myspace, Squidoo and Gather are the best sites which I use.

Every community is different, and each has unique goals the campaign focus should therefore meet the needs of the community, before the needs of the marketer.