Well, you can argue RT is more prone to spam because there is less (recent) data and therefore spam filtering is harder. However, with Twitter/social networks

Well, you can argue RT is more prone to spam because there is less (recent) data and therefore spam filtering is harder. However, with Twitter/social networks the accounts have reliable authorship/history and you can exploit that for filtering... basically rank higher the pieces of data from old accounts that didn't spam before. I wouldn't say spammers have inherent advantage for real time. Google has been pretty good in figuring out what to include in their "universal" search, I guess their quality control will notice if RT results are not useful for most people.