`meta.stackexchange.com` and `meta.com` are not titled the same.

If one is concerned about infringing trademark, one can search the [trademark database][1] in the relevant jurisdiction.

`facebook.stackexchange.com` could exist. There are other trademarked product names that are used as subdomains to denote product-specific Stack Exchanges:
- https://arduino.stackexchange.com ([trademark](https://tsdr.uspto.gov/#caseNumber=77708806&caseSearchType=US_APPLICATION&caseType=DEFAULT&searchType=statusSearch))
- https://magento.stackexchange.com ([trademark](https://tsdr.uspto.gov/#caseNumber=77521711&caseSearchType=US_APPLICATION&caseType=DEFAULT&searchType=statusSearch))
- https://mathematica.stackexchange.com ([trademark](https://tsdr.uspto.gov/#caseNumber=76263348&caseSearchType=US_APPLICATION&caseType=DEFAULT&searchType=statusSearch))


  [1]: https://www.uspto.gov/trademarks/search