I created a Myspace page earlier this year to soley promote my work. I've built up a nice size 'friend' list for the short period of time that I've been out there, but I can't say that it has directly contributed to any sales of my book. At the least, I can say it's another (free) way to get your book and yourself as an author at little more publicity.
It's easy, fast to do. If you have anyone who can help you invite and approve friends, the ability to post to the "bulletin board" will spread the word about anything you want to fast. For National Invisible Chronic Illness Awareness Week we got over 2500 friends in a few months and had over 30,000 people come to our (the sponsors) of the week, website, www.restministries.org. I also posted requests for book reviews and had a good number of people who actually asked for the book (it was pretty inexpensive and we are our own publisher so I was able to send lots of review copies)...and they wrote some great reviews and posted them on their blogs, MySpace sites, all over. I always thought MySpace was a "waste of time" but I will always keep it as part of my marketing plan as long as it works. It mostly depends on your topic. W/ illness, we have a huge audience over there.
I find it useful to post the bulletin of my new releases or reviews, etc. Feedback from that is worthwhile.
We can never be sure whether it helps sales, but honestly, just getting your name out there and letting people see it and connect to you.
Guys...We have created "The Free Online Community of Authors, Writers, Poets and their Readers" It is specific to the business of writing. We hope that it will become the myspace of the writing community.
One thing I have noticed about MySpace is that keywording your page is hugely important. Many 'spacers' do searches on Google and other search engines, looking for specific friends in certain parameters, i.e., Vanilla Heart Publishing, one of our imprints, is a more mainstream fiction and non-fiction site and we get a few visitors and interested authors, as well as sales.
Caged Heart Publishing is a bit more uh, non-mainstream, meaning we publish kink and erotica as well as alternative lifestyle non-fiction, and we get many sales, a few legit author queries, and plenty of traffic.
I will say that the main thing MySpace and Squidoo can do for authors is to get a higher page ranking and SEO numbers, and that is nothing but good for sales and for credibility.