For sure they're not standard, I just replied to "never seen an apartment this small" and wanted to point out that in some cities they're not unusual.

Another example - Paris, 87 ads for condos 0-20m^2 [0], 104 for 30-40m^2 [1] on pap.fr, a popular site. Similar numbers for rentals ("location").

[0] http://www.pap.fr/annonce/vente-appartements-paris-75-g439-j...

[1] http://www.pap.fr/annonce/vente-appartements-paris-75-g439-e...