Robots.txt and Adsense

[morpheus83]

Google advices not to use robots.txt for optimum adsense performance. Any specific reason.

[jetteroheller]

Google advices not to use robots.txt for optimum adsense performance.

Where do You imagine that Google would do this?

[DumpedbyG]

Where and when did Google advice this?

[morpheus83]

Acceptance mail from adsense
STEP 1: Activate your account.
Please visit [google.com...] . Log in to your
account using the email address and password that you submitted with
your application, and agree to the AdSense Terms and Conditions.

STEP 2: Paste the AdSense code into your web pages.
Just follow the instructions on the 'Ad layout code' and 'Search code'
pages to copy-and-paste the Google code into your site. Google ads and
AdSense for search will begin running on your pages within minutes.

STEP 3: See the results.
After your ads start running, you can see your earnings at any time by
checking the online reports in your account. Please note that you might
not maximize your earnings from AdSense if you have any of the
following on your website:
* robots.txt
* frames
* forms and dynamic content
* excessive images
* login and password requirements

[guitaristinus]

"Please note that you might not maximize your earnings..." (my italics)

Some people may write their robots.txt wrong, keeping Google from crawling site. What are some other reasons a robots.txt might hurt earnings?