And there lies the rub. You can't verify if they do or don't embed such content. These companies are just like "trust me bro".
The spying and tracking started pretty quickly though and they've repeatedly demonstrated that they can't be trusted. They've even violated the law on several occasions in efforts to collect data they had no right to.
"If you have something that you don't want anyone to know, maybe you shouldn't be doing it in the first place." - Eric Schmidt CEO of Google