Ok so I have this site/blog, but also wanted to go after other topics, say "dating" etc.. Should I create different blogs for different topics or does it really matter that much??
do niche specific blogs which you can promote toward specific audience. all in one blog doesn;t really say much and doesn't appeal to anyone since its not focusing on anything. if you can do a good job on niche specific blog, then you will have repeat visitors and RSS subscribers which will be very useful
it is better to create several niche blogs than putting them into one blog for better ranking and indexing.
I aggree with all of you... You can use wordpress mu then put it on your domain, use subdomains for specific topics or niche... easy to manage and you can add some of your bestfriends, tell them to blog for you! hehehehe I use the "all-in-one" for big traffic then I use specific niche for those who love some things like entertainment, makemoney, and gadgets. If you use "all-in-one", you will get more traffic for organic keywords!
I use WPMU too. But I install the Domain mapping plugin so I can manage top level domains from just one installation of wordpress. I got 25 blogs with domain mapping right now ..works great.