Running 30 blogs is a huge waste of time if you are doing it because you think that the links will be valuable. Links from those blogs will only be valuable if they attract their own unique links from outside of your network of sites.
If you can produce content that will attract links then put that content on your main site so that it gets full benefit from the links and not the small benefit that will leak out of a blog.
* "It's not the size of the dog in the fight that matters, it's the size of the fight in the dog." Mark Twain
* "Free advice isn't worth much. Cheap advice is worth even less." EGOL