[dredge]

From my experience, when Google de-indexes a site, they also suppress any PageRank the Google Toolbar would have shown for it; that doesn't appear to be the case here, digg.com is still PR8.

Having toolbar PageRank[1] and yet no cached page[2] is not something I've seen before.

[1] http://toolbarqueries.google.com/tbr?features=Rank&sourc...

[2] https://www.google.com/search?q=cache:digg.com

[jasongill]

Your experience may be limited, because this is very common. PageRank and indexed status operate independently of each other; it's not uncommon to see a site that was deindexed still maintain PR for quite some time (and often, indefinitely). However, if your site is deindexed, PR means "nothing" because your links no longer provide juice.

Valid PR while being deindexed is one of the (many) tricks that Google has added in the last couple years to try to reduce the usefulness of getting PR for blackhat purposes