Two Reasons Why A Blog's Pagerank Down After Template Changing

I visited my friend blog and his blog pagerank becomes 0 after 2. He said "Template can decrease our blog pagerank". I agree with his statement because it is really happened to him, but may be some bloggers did some mistakes which make their blog pagerank down. Two reasons why a blog pagerank down are :
1. Bloggers forget to verify their blogs in Google Webmasters Tools. Remember that in a new template, your verify code is not included there. This blog doesn't have pagerank whereas in end of may google pagerank updated. Why ? I think because of I often change this blog template, and I forget to verify this blog again.
2. Too much template designer's links in template. If you download a template and use it as your template you will promote template designer's links, you can find them usually in template footer. If too much dofollow links, your google pagerank will decrease.