I think mini SD (sdhc) is the lame duck of the SD formats. Normal size SD cards offer more capacity and microSD cards are more portable. i.e. Using an adapter you can make it fit any SD format size. I'm surprise Nokia just didn't put a microSD card slot on the N810 or two microSD card slots instead of the miniSD slot.

I haven't seen or heard announced any 16 GB mini SD cards. Not many devices use them natively outside the N810 and some older cell phones.