Why Google PR going up and down?

Few weeks back, Google PR did an update, many new bloggers getting a good PR for their blog. Mainly those blog with less paid posts are being promoted (as what I noticed). But for many also got the PR demoted, especially for blog host at Blogspot with paid posts. I can't run away from that, from a good PR 3 dropped to 2.

2 weeks later, Google do an update again. Can it be so soon? it suppose to be update every 3-4 months right? A few bloggers already start making noise their PR is fluctuate, sometimes shows N/A, sometimes shows 0. But what we can do, their update period is so short now.

Everyday I keep my eye close in checking the PR meter. It has been in PR2 for about 2 weeks and today I got a BIG FAT ZERO!!! Is this the penalize we got for doing paid posts? Blogging for money need a good PR, but Google don't give blog with paid post with a good PR. Now they are trying to give all of us a ZERO, even for those with less paid post also deserve a ZERO now.

So you tell me what can we do now to get a PR and keep doing paid post? If you always find the PR meter not functioning well, you can try this PR checker from 3P very accurate.