I have no inside knowledge and I speak only as a research student working on search engines, but my guess would be that Facebook and Twitter don't allow their pages to be crawled[1]. If I recall MS had to strike a deal with both of them so that Bing could use them in their results. Another "problem" is that the notion of document relevance varies from a "standard" web page to a social network[2], and mixing them up on the same result page could be confusing.
[1]: a good social search would need realtime access to the API of those websites, which is why you still see "some" content like FB profiles in Google's results.
[2]: what I mean is that you have additional parameters to take into account: incoming/outcoming edges, "status" of the author, additional metrics of popularity, redundancy of content... Social search is an entire research topic of its own.
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I have no inside knowledge and I speak only as a research student working on search engines, but my guess would be that Facebook and Twitter don't allow their pages to be crawled[1]. If I recall MS had to strike a deal with both of them so that Bing could use them in their results. Another "problem" is that the notion of document relevance varies from a "standard" web page to a social network[2], and mixing them up on the same result page could be confusing.
[1]: a good social search would need realtime access to the API of those websites, which is why you still see "some" content like FB profiles in Google's results.
[2]: what I mean is that you have additional parameters to take into account: incoming/outcoming edges, "status" of the author, additional metrics of popularity, redundancy of content... Social search is an entire research topic of its own.
Twitter tweets show up quite often in search results
of course they let themselves be crawled..have you never seen facebook or twitter pages in search results??