I'm having trouble finding any recent info on this question. Is there an advantage to using subdomains instead of a folder structure?
If it's all on the same topic, then you'd benefit from using subfolders (Google, for example, takes into account the content and keywords of the other pages on the site when ranking any particular page). If it's a different topic, then definately a subdomain. If it's in between, then whatever suits your fancy.
Yea. I messed up with that on mystikmedia.com when I added the Link Checkup product. I should have added it on a subdomain or new domain. Shortly after it started getting so many webmaster related backlinks, my other mystikmedia.com pages I was targetting on that domain (mostly graphics software related) stopped ranking well. They are back a little now, but still not ranking as well as before (in the top 50 now; top 10 before).