is it a waste of time to network your sites together unless...
 

you have them spread over several different class c ip's?

No. Forgetting search engines for a minute, surfers find *your* sites easier if they are linked together.

well yeah i guess i should of said is it advantageous in regards to search engine ranking. i've heard some say it really doesn't make a difference and some say google devalues sites linked together all on the same ip.