Matt Cutts, the head of Google’s Webspam Team, answers the question, “Why does Google crawl/index blogs (specifically sites notified by ‘WordPress/XMLRPC pings’ so much faster than a ‘normal’ site submitting a revised sitemap? What is the impact of that on the overall ‘quality’ of the index?”.

What Matt Cutts intently discusses is that crawling is not indexing; they have very distinct functions and goals.

Submitting a sitemap does not guarantee that Google will crawl a particular site. Moreover, what a sitemap actually does is to help Google’s spider to discover new URLs and for Google to make canonicalization decisions to help improve Google’s main index of web pages and content.

Cutts sites an example in which blogs who ping Google gets crawled soon after an update. According to Cutts, often it is the Google Blog Search spider that answers to pings from blogs. A blog post may show up on the Blog Search results, but it does not mean that it has already been included in the main Google web index. Just because a web page gets crawled does not automatically mean it is also indexed.

In the end, Cutts was strong in his point that making great content and getting well known (translation: being an authority in a particular field of interest) are two sure ways of having Google crawl a web site more often.