"you acknowledge we may not always identify paid services, sponsored content, and commercial communications"
Translation: You accept that we may try to trick you.
I'm an intellectual property lawyer and I think the intent behind the above language is quite clear. It is not aimed at alleviating an undue burden of identifying commercial content (as Instagram might suggest), it's about reducing transparency to allow for marketing tactics that would not likely be viewed favorably if they were obvious to the user. While under no legal obligation to do so, Google has been identifying sponsored content for over a decade. If we were to begin by looking at "standard practice" then we might start there.
I think it's great that people are reading TOS from web companies and making their concerns known. We might call this negotiation. If you accept that idea, then I think users are in an excellent bargaining position. They can walk away at any time. They can adapt and they can find new alternatives. These companies however may not be able to find new audiences so easily. I believe they will take the feedback very seriously and respond, with new language if necessary.
I'm noticing some of my friends on Facebook who were using it extensively for one purpose or another are now closing their accounts. Other friends of mine cannot use Facebook because of their employers. It seems clear to me there are both costs and benefits to using Facebook or Instagram and that sometimes the costs may outweigh the benefits.
Keep reading TOS. It is good for the web.