I am abandoning the idea of using one SIM both for voice and data - I'm presently using two plans from different telcos, one for voice (and it's a bargain) and one for 3g (4,77 gigabyte/month for 30 euros).
So by now I bring with me two phones plus my n810 - that's really too much. This is the reason I'd embed my data sim into a not-so-large kludge sticked to the Pandora... (or else, as lcuk suggests, into a maemophone).


EDIT: here's the Pandora Photo Album -> drool