Off-topic, but this ongoing trend of brands getting TLDs is really starting to infuriate me. It's not what TLDs are for! Sony is a Japanese company, so it should use sony.com or sony.jp.
There's no inherent reason to restrict the number of TLDs. The best way to combat rent seeking from registries is to allow any organization that has the technical capability to operate a registry.
Why do companies and organizations get special treatment over regular people? I think a simpler fix is just to ban any companies that register domains from squatting on them.
The bigger problem is the rent seeking some registrars are doing now by increasing prices. Not sure what domain portability might look like (maybe requiring multiple registrars per tld), but something like it would solve this problem.
EDIT: I couldn’t have been more wrong — all three have TLDs. Not really sure if they are being used for much though! Most of the action still seems to be on their .com domains