Several users have reported an issue in which photos taken with the iPhone's built-in camera will not save to the device, vanishing immediately after they are taken.
The most successful fix for this issue we've seen thus far is as follows:
Restore your iPhone using iTunes, but do not restore custom settings data from the computer-stored backup after the restore process is complete. Do not set up as a new iPhone, and do not restore from backup -- just disconnect the iPhone when prompted to make this choice. Note that you'll temporarily lose text messages, notes, call history, contact favorites, sound settings, widget settings, etc with this method,.
Try taking a photo -- it should properly save to the device.
Connect your iPhone again, and in iTunes, restore your personal information from the backup when prompted.