[quote name='SteveMcQ']500 pics? Depending on the size of the image I don't think you can get that many on even a 1GB card. Well, at least at 5MP. IIRC, the 512MB memory stick that I use for back up only gets about 100 5MP images. 3MP gets you 150 images.[/QUOTE]
Sure but 5 MP is still pretty high for a lot of people using inexpensive cameras. Depending on the media used the limit is the capacity supported. This was a big problem with the inaccurately named Smart Media. If the camera wasn't designed to handle a card above a certain size, then at best it would give an error. At worst, it could crash the camera in such a way as to require factory repair. I had this happen on an early Olympus model. We were getting ready for a trip to Germany for a job where digital photography was essential. We had 4 Megabyte cards for the camera but 8 MB cards had just dropped to a very affordable $10 per megabyte. (Ah, nostalgia.) I picked one up and tried to use it in the borrowed camera where upon it immediately went into an incurable coma. Really bad firmware design.
More recently my sister started using an obsolete Vivitar model she'd gotten for under $100. Adequate for here purposes but the 8 MB of built-in memory was limiting. This unit also take Smart Media but the manual and their customer support people had no idea what the addressing limit was for that camera. I found a 64 MB Smart Media card at Fry's for only $20 and took a chance. Fortunately it works fine and my sister can now take more shots at maximum resolution (possibly 2.5 MP) than she'd ever expect to need in a day. So she's happy at little expense.
If it was a Compact Flash based camera there wouldn't be any issue. CF has a built-in IDE controller, so there is no effective limit on card capacity until you come up on the 8 GB limit of FAT. Most older cameras don't know FAT32, so 8 GB would be the limit, even though it would require external power or many battery changes to fill it up using the best quality mode of a camera that old. My experience with the Olympus made me highly appreciative of how CF works.