I have no plans to actually move to Sweden, and no current plans to return (though it's not unlikely that I will at some point), and so the +46 number I have will most probably sit idle, the SIM card in a drawer next to the German card I bought in Berlin last year (unlike that one, though, this card can be topped without having a local bank account in the country in question, making it more likely that I'll reuse it). But at the moment, the SIM card is in my iPhone, providing me with access to maps and similar services on demand, and my British SIM card is in my second phone (a Palm Treo 650, a piece of mid-oughts executive power-tech that looks ridiculously clunky these days and probably will be considered retro one of these decades).
The reason I went to the somewhat absurd extent of investing 99 Kr (almost exactly £9.90) in a foreign telephone number I will use for a few days is because of the unusable state of data roaming in 2011. While, in the EU at least, roaming charges on phone calls and text messages have come down, data still remains prohibitively expensive, with the foolhardy user who enables data roaming on their smartphone likely to drain their prepaid credit in minutes or, if on contract, be on the hook for thousands of pounds.
Things have improved slightly, though not enough to make using a smartphone abroad with one's own SIM card remotely economical, except for the super-rich and those with the deepest of expense accounts. For example, Vodafone (my UK carrier) now offers either 5Mb or 25Mb (depending on the country) of data abroad for £2 a day, with subsequent use being charged at £1 per megabyte. I tried using this when in Paris a few days ago, and found, to my chagrin, that the quota evaporated within ten minutes of idle time. Presumably Vodafone's offer is intended for users of something other than modern smartphones. Not quite sure what: perhaps those social-network featurephones marketed to teenagers with limited allowances?
I suspect that this has less to do with smartphones sucking up vast quantities of data and more to do with the way roaming data being metered being incompatible with the way smartphones use data. I imagine that what is happening is that, for billing purposes, one megabyte is one megabyte or part thereof, and the clock stops whenever the phone stops sending or receiving data for a period of time and/or when the phone connects to a different server. Which was probably fair enough a few years ago, when the much simpler phones did one thing at a time, and internet access on phones was an afterthought, a special mode added on after the fact. Today's smartphones, however, are entirely different beasts, being effectively UNIX-based computers designed to be permanently connected to the internet, and constantly sending and receiving small quantities of data, from notifications to location hints. Because this data is sent as internet packets, a premium-priced service on top of the mobile phone network, the partial megabytes soon stack up, and so does the bill.
With smartphones, we're living in The Future, but only in our home countries. There, we can pull down maps, check email, upload photos to the web, and even, particularly ironically, get spoken text translated into other languages. Elsewhere, we're still in the mid-2000s, forced to rely on pre-cached data and scrounge for open wireless access points (themselves an increasing scarcity, due to the three apocalyptic horsemen of terrorism, paedophilia and copyright infringement). Of course, one can, for a tenner, buy a new SIM card, and then freely use the same networks one would otherwise be paying through the nose for, at the cost of losing access to one's phone number for the duration. Which, all in all, is an absurd situation, and The Future won't officially arrive until this is resolved.