I like the thought of "follow the money"... It sure makes you think when G is spending money on this application. The reason though they are spending money upon the application in my view is so they are able to obtain, quantify and catalog user data including browsing patterns, clicks, etc. PR in and of itself has little to none important for search engine positioning.
Pagerank is important for the link building process, the higher the PR, the more the chance you can have inbound links But sometimes PR is not that important, traffic is more important than the PR
Traffic (with conversions) is always more important than anything else. PR itself shows officially (you can show it to anyone else) your credibility, really Oh and as for the question, I already told it somewhere here. I know a Czech site with gaming content getting more than 1.000.000 hits monthly (now i don´t know if from SE only or overall, anyway) with only PR4, which you really get for your mainpage if being listed in DMOZ and some 20 - 30 free directories.
People say PR is not important because Google can take pagerank away from your site at any time for any reason. It's just too unstable to have any sort of value IMO.
PageRank is important from a buyer/seller's point of view, but it's really only a bit of a clue as to your actual backlinks. It's important to stay up on all widely used rankings.
People who say it is not important have sites with low PR. Of course is important. Internet giant is evaluating your site and it assigns some "importance" number. Not important? Do not kid yourself. They spend millions to perfect their algorithms and people say it is not important. I don't get it. How do you put a value on a website you know nothing about?: The amount of traffic it attracts, backlink profile it has, alexa ranking and of course you are going to look at Google PR.
I have two PR7 sites and several PR6's. I say it's not important in terms of rankings. It only becomes a real factor when selling links - which I don't do. Trustrank is far more important, and we can't see a value for that.
How do you know what my definition of excitement is? For me it sure isn't a PR update. Excitement for me was for example when I made $460 in 24 hours.