I believe DDG uses Yahoo! BOSS (http://developer.yahoo.com/search/boss/) as one of its primary indexes (check out DDG's FAQ). BOSS is a pay per use model (as due to Yahoo's deal with Microsoft, BOSS needs to charge to cover cost) - so it benefits Yahoo! directly. Also, now that Yahoo is out of search crawling/indexing business, it is not really concerned about DDG becoming a competitor - in fact it is a validation of the BOSS model which is something Yahoo will like to promote.
That's right. A couple of other data points. a) Ask/AOL also don't have crawlers and have significant share. b) There are a few places to get a decent base page rank feed now, and it appears to be increasing.
