I read on Tech Digest yesterday (here) that now R4 DS cards are illegal. If you don’t know, the R4 DS card is the same size as a regular DS card, but with a microSD card slot. This allows you to put homebrew software (or commercial ROMs) onto the card to play on your DS.
I don’t know if it’s illegal to posess one, but the post I read suggested that it was illegal to sell or advertise them in the UK. Lucky I already got mine in March this year! Here
This has had a knock on effect that sellers appear to be selling R4 DS cards as cheap as they can, to try and get rid of them!http://www.memorycardzoo.com/1713/R4/R4DS-(v2)/R4-Revolution/ under £3