I've read to format the card IN the camera that will be using it. The different "speeds" of cards will list their write speed in MB/sec. I don't know about .jpeg for instance but for raw files for my Canon XSi I've been told I would need an 18MB/sec card to keep up with continous shooting in RAW format. It's camera specific though due to continuous shooting speed and the megapixel rating of the model in question. Of course, if you're just taking one picture here and one there and no fast speed continuous then really you don't need a high speed card from what I understand. As far as brands, when I was at the camera shop where I bought mine we were talking about them and they mentioned that the majority of the cards have a max of about 5000 writes (new pics, delete, formatting, etc.) before they start going. They said the Sandisk cards though are rated for 200,000 writes.

I know flash cards do have write limitations, and knowing Sandisk has been in that business for a while I can see that as being pretty accurate though I haven't looked up specs myself. I'm pretty sure they weren't just trying to sell me a Sandisk card either since before the conversation I told them I planned to buy my memory cards for the camera elsewhere. They just offered up the brand/speed info as advice for what to look for at that point.