If you owned a blog or a forum or a site where your visitors can left messages, what would you do? Would you allowed them to post do follow back links or not?
It's true that if you enable do follow back links there will be many spammers who will try to get this advantage to increase their Page Rank. They can cause you mess with the manage of the comments or if you don't have time to moderate, they will be shown to your page, something that is not so nice..
On the other hand, allowing only no follow back links, can cause you many value comments, as many honest webmasters are looking forward to make value comments on do follow sites. Some of them are ready to do link exchange too, but when they realized that the owner is not giving do follow back links, they hesitate to ask..
Which is the best option?