Gary Illyes from Google responded to a question in the Google Webmaster Help forums about hosting your content on a CDN, content delivery network.
The question was why did Google assign a special crawl rate to his site.
Gary from Google said, Google may assign content hosted on a CDN with a special crawl rate. He specifically said you should most likely never increase the crawl rate manually if you are on a CDN, at best, leave it for Google to decide. You can lower the crawl rate, but do not increase it.
Gary from Google explained:
When you're using a CDN, we may assign a special crawl rate for your site so that we can crawl as much as possible without affecting negatively others who're using the same service. It's best to not tackle that setting, especially since we're already accessing your site more than 4000 times a day.
If you want to lower your crawling rate, let me know, but I definitely not recommend increasing it. I'd rather focus on posting unique and compelling content and on user experience.
More on CDNs and SEO:
- Amazon Elastic Load Balancing & SEO Considerations
- Does Google Index Content in "The Cloud" (Amazon S3, etc)
- More Tips From Google On Content On CDNs
- Google On Content Delivery Networks & Search Rankings
- Should You Host Images On Your Domain or Flickr For Best Traffic Potential?
Forum discussion at Google Webmaster Help.