Why does my doorknob need to be connected to the internet? Does my fork need to be connected to the internet as well? How about my shelf? Or my towel?
And if they are connected to the internet, who is collecting that data? Is it secure? What will it be used for?
So you can pay to use it: https://pbs.twimg.com/media/B9XFnbFIMAEj8rF.jpg
Burglary perhaps.
> Or my towel?
Germs data collection perhaps.
> And if they are connected to the internet, who is collecting that data?
Whoever you authorize it to, perhaps.
> Is it secure?
I doubt it will be 100% secure.
As to your questions - great questions, and the answers will be great opportunities to start/grow companies. "Who is collecting the data" and "is it secure" already are, "what will it be used for" will be in 5-10 years.
"We are in great haste to construct a magnetic telegraph from Maine to Texas; but Maine and Texas, it may be, have nothing important to communicate."
There won't be a door knob. The sensor will be in the door which will slide open for you when you are near but stay locked for everyone else.
Some of these things are already being done by people later they will be common at least for the people that can afford them.