Google Adds, Then Pulls, Advice Not To Block Ad Landing Pages From Its Crawler

On Wednesday/Thursday of last week, Google added a new guideline to their Webmaster Guidelines to “not block a destination URL for a Google Ad product” via your robots.txt file. 24-hours later, Google reversed that guideline and put the webmaster guidelines back to exactly how they were Wednesday morning.

Here was the addition and then what they removed:

Make efforts to ensure that a robots.txt file does not block a destination URL for a Google Ad product. Adding such a block can disable or disadvantage the Ad.

We asked Google why did they make the change and then later, when we noticed the guideline was reversed, why did they reverse it?

Source:http://searchengineland.com/google-adds-pulls-advice-block-ad-landing-pages-crawler-184506