[jpetazzo]

> [is there] _any_ hack that allows us to limit the size of the filesystem?

Docker 0.7 will let you do that, since each container will have its own (thin) block device, and therefore have a default size limit (which can be trivially bumped up if needed, of course).

Now to anticipate your next question (assuming it is "when will Docker 0.7 be available?"), the answer would be "pretty soon", since the core team is ironing out the last issues before merging to master and releasing :-)