Its around a couple of days that i searched (googled) about the pagerank and came to know that the blogger world is suffering a drawback of the field of pagerank.

Every blogger has its own theory.

Some told it as an algorithm change by google.

Problogger and Copyblogger, two of the most popular blogs on the niche, announced that their PR dropped from 6 to 4. Previously other authority blogs confirmed that they lost PR

Previously other authority blogs confirmed that they lost PR, but the suspect was towards paid links. Given that Problogger and Copyblogger are not selling links, it might be just a readjustment on the PR scale. Some people are arguing that since the PR drop is not generalized, it must be a slap from Google due to practices that conflict with its guidelines.

the sites that got penalized were either selling links or exchanging them inside large blog networks. This is a feasible explanation given that most of the Weblogs, Inc blogs (Engadget above all) were penalized, and they do not sell paid links either.

But there are others who believe the other way.
“Paid inclusion is a search engine marketing model in which Web site owners pay a search engine company to guarantee their sites will show up in search results.” But then this definition changed when this process of buying links spreads from search engines to individually run websites and blogs. Companies started preferring to have their links shown on a blog having higher visitors or Page Rank with more visibility i.e. having a small banner on side bars of a web page or a banner at the end of the article. Now according to Page Rank Theory , each web page having some Page Rank pass its juice equally to the links placed on that page. Someone then publish a theory that High Page Rank is effecting your ranking in Google SERP’s. After this a new era of paid linking starts. People start placing their adds on the webpages having high Page Rank. This situation alert Google About its Paid Link Program known as AdWords and it start yelling that Paid Link.

Whatever be the reason,i want to ask about the future of companies who pay per post to the bloggers.

This is because after such an incidence,the companies who were paying to put the link in review were now paying even more (as much as 100$) to remove the link.
So,blogges,play the game safe. :)