i have 2 but i'll soon have 3. One of them is just a place to yak, the other i try to keep for more serious subject matter and the third will be non free hosted and will be very much a niche blog. I'm really excited about it.
I only have one, and I don't know how I'd ever find the time for another one. I spend so much time on my current blog that I KNOW I'd be overwhelming myself if I tried to add another. Because I post several times a day, I spend a lot of time researching and writing, then promoting those posts. Too much to take on more than one. Lately, I've been posting once a day on Monday, Wednesday and Friday because I'm doing a series, Green Rooms in a Box. Check it out: http://www.greenyourdecor.com/?cat=1028
I have 3 blogs. I started out with just 1 and had all of the information jumbled in there and was posting 2-3 posts a day sometimes which was far too much for my readers to go through so I decided to branch out the different information to 3 blogs and people could subscribe to whichever one they were interested in.