It makes you vulnerable to MITM attacks, since when you connect to your camera, you can't be sure it's actually yours and not just another device with the same well-known certificate/key.
It means that if you use a key exchange mechanism that encrypts the session keys with the server key then someone who's extracted the private key from one of these can decrypt communications with any of the cameras using the same certificate/key.
If you use a key exchange mechanism with forward secrecy, extracting the private key wouldn't allow Eve to decrypt all your communications.