Ah, no, that's exactly what it is.
Fresh from my ordeal of spending four-and-a-half hours trying, and failing, to reach the new foreigners' health check centre (now located many miles OUTSIDE the city), and my consequent abandonment of plans to renew my visa, immediately upon getting back to my apartment yesterday I learned of a new campaign by the Beijing police to 'crack down' on foreigners "working illegally or overstaying their visas".
To this end, the police are planning to blitz the areas most frequented by foreigners - Wangjing/Lido, Wudaokou, Sanlitun - with spot checks demanding to see our passports and residence registration certificates. Theoretically, there has always been a legal requirement for foreigners to carry these documents (since we don't have any local ID), but no-one - least of all the police - has ever given it a second thought, since it is obviously a completely fatuous idea that we should risk losing our passports by carrying them around with us all the time.
I imagine that, as with the pre-Olympic 'spring cleaning' of the city, this asinine crackdown will initially target Africans (many of them are highly visible in selling drugs around the bar district; hence, unfortunately, all Africans get stigmatized by this). But it could soon become a hassle for everyone. It does sound as if the authorities are pretty serious about this; and the campaign is slated to last for 100 days. I'm glad I'm going to be out of the country for at least 90 of those.
For my last week here, though, I am going to spend as much time as possible in Wudaokou and Sanlitun, sidling up to coppers and defying them to ask me for my passport. I really want to have an opportunity to piss myself laughing at them.