SandeepRa - 7:30 am on Dec 29, 2011 (gmt 0)
In my opinion guest posting benefit both ways, it benefits the guest writer in the form of backlinks and it benefits the website owner in terms of traffic. Because if the post is quality, it will surely get visitors.
But make sure that you allow only those guest posts that are of same theme and are providing quality content that would appeal the user. Approve the guest posts only after reviewing them properly.