Google announced those "improvements" to shopping results on May 31 and said by the end of the year its product search results will be limited to paid advertising and be called Google Shopping. It said this would lead to better shopping results for users because "having a commercial relationship with merchants will encourage them to keep their product information fresh and up to date."

Katz isn't the only one who takes issue with how Google is doing things these days.

"[P]aid inclusion was one of the original sins Google listed as part of its 'Don't Be Evil' creed. But these days, Google seems comfortable with paid inclusion, raising potential concerns for publishers and searchers alike," wrote .

Singhal says Google clearly labels its ads and commercial experiences as such and that they're not mixed in with unpaid results.

"This is in contrast to most comparison shopping sites, which receive payment from merchants but often don't clearly label search results as being influenced by payment," he wrote.