I went to digpagerank.com and was exploring PR of sites. I stumbled upon blogspot.com's PR as ZERO. What do you think? Why did it happen to blogspot.com, which is owned by Google itself?
Your question doesn't make sense. If you mean that that is a subdomain of blogspot then ok. A different pagerank is assigned to each page of a website, so blogspot.com doesn't have to have the same pagerank as it's subdomains. Go to http://blogspot.com and look at the address bar, it redirects you (and thus the pagerank is forwarded)