the golden rule with crypto. always do research. there are way too many people trying to sway opinion one way or another online.

You are right, more often that rating just confuses you since it doesnt show the right value of the project. I think Datum got a lot of attention doing the giveaway for promotion of their project and it looks like it was worth it.

afaik there is no demo app yet, but i assume that it will be available to the public as a beta maybe in the near time?

Well I hope our data will be used for the good in the future. I can imagine that our medical data is worth a lot of money to certain firms (like insurance, big Pharma, etc). Currently we don't know if Apple for ex is selling the HealthKit data (they claim to safeguard our privacy with that), but does Google keep our health data private? I don't think so, as Google only makes money with selling information, they do not actually have products of their own (like iPhone and so on) ..
I still think it's a plus if we can sell our data. Safeguarding is imho no longer possible.. These smartphones we are carrying are just small spyboxes

In the whitepaper there is mention a marketplace. From that word I get the impression there is interaction from both sides. But you are saying that the marketplace is for data consumers to browse through and the users have no say in it?

They should have launched their alpha version on August 11, 2017 according to the roadmap.
Or maybe the alpha version they meant before wasnt about demo.

its a good option, there are some option to share data.
so, your data is save if you only share with specified consumers, if you believe with consumer, its not problem.

i think, this program is relevant with shop with delivery order, if you need order some product but you wont anyone know what your order, its only shown for you and the customer if you share it with specified consumer options

Well, there is no problem in selling personal datas if the user accepts it. The problem if the treatment or the personnal datas and the way they are recolted.

That's actually what some careless people have been doing the whole time   

I didnt get any information about that so far, but i think they really need it to make sure that they already have some early users and maybe to attract other people (in this case , this is about marketing)