Google last Tuesday implemented previously announced changes in AdWords, creating a minimum bid for each keyword based on a quality score assigned to it - and though the change also allows advertisers to reactivate keywords disabled because of low click-through performance, some advertisers are complaining that their costs have increased, writes CNET. On the other side of the equation, website publishers are generally praising changes Google has made because their revenue is increasing (as is Google's).

Some advertisers have complained that instead of paying 5 cents, they have to bid anywhere from 10 cents to $1 or more for new keywords - and they say Google is not being transparent about how it determines the quality score.

Danny Sullivan of Search Engine Watch is quoted as saying that even with the higher bid prices advertisers are getting a big return. "This is part of the evolution of these ad systems," he said. "They started as low-cost systems, and it is only natural that they would increase the prices."

Meanwhile, publishers have reported seeing an increase in revenue from AdSense ads on their sites. An entry titled "Fewer Ads, More Money?" on the recently launched AdSense blog said Google had updated AdSense to decrease the number of text ads that appear in ad unit, and "we saw that the increased user attention to these relevant ads resulted in a higher CTR [click-through rate]. This means more revenue for publishers."

Yahoo recently launched a beta of Yahoo Publisher Network - a significant challenge to Google's AdSense program.