In March, Yahoo rolled out its new Site Match paid inclusion program, which quickly drew wide-spread criticism. It was a terrible blow for Yahoo in its quest to win searchers away from Google. The move infuriated plenty of advertisers, as well.
Google believes payment has no role to play in fixing its crawler problems. It views any payment linked to its crawler-based results as potentially tainting those results. Instead, it seeks to solve its flaws purely through unpaid means.