You mean they decided to use advanced spam filters that were already used by small sites before other large sites decided to care about the problem? On some cases, a couple of weeks before.

Gmail has the worst spam filter of any email provider I use today, excluding the one email server I have running on my domain that gets almost no email and has no filter. Or, well, spam filtering is a lesser problem on my server too because it doesn't block nearly all the email that I care about.