Hard to tell, really. From my experience it is ok to blog on subdomains,
as long as you keep the topic and content unique on each blog.
Having nylon.myhost.com and nylons.myhost.com might be no good idea
if the content is also similar. On the other hand, look at freebloghosts
like sensualwriter... it also works with subdomains for them.
Personally I'd use as much as I can from my webhosting, so every single
domain has several subdomains. Sometimes when having a great domainname
like freepornhost.com it is a great advantage to have subdomains as the keys
free and porn are indexed with it.
Good luck and sales
aj