your profile page is located on stumble and will naturally get a page rank. However links on that page are "no follow" and as a result will not receive any "pr" juice. Hence it's of little value to anyone for "PR" purposes.
I registered a couple different StumbleUpon accounts for my different computers (wife, kids) but didn't notice that the user page has PR. I've been submitting a lot of my sites and pages to StumbleUpon recently and have gotten some hits now daily... do you think it will last? Eric