Why Pros Should Consider Nothing Larger than an 8Gb Micro SD Card
Many professional photographers will only use an 8GB Micro SD card or smaller. This seems strange to many people starting out because it seems inconvenient. While a large memory card makes it easy to take hundreds of photos without needing to change the card there are problems with doing this.
Loss of Card
These Micro SD cards are tiny. This means that they are very easy to lose. If you were to lose them then you would lose all of the files on that card. If you lost a large 16 or 32GB card then you would lose thousands of photos. By using smaller cards there isn't as much of a problem by losing one card. In other words, this is limiting your loss.
Because all of these photos are stored as digital files there is a risk of corruption. If the SD card becomes corrupted then all the photos on it will be unreadable. To prevent this being a problem you will be able to use smaller cards. By using smaller cards if it does become corrupt then you won't lose as many photos.
Tried and Tested
Any memory card which is 8GB or smaller has been out for a good few years. This means that the technology is tried and tested. This also means that it's very reliable. Larger cards are much newer and may have faults.