There is a difference between abusing a relational database versus using something that is key-value from the ground up.

Notice how in the example you have:

  1  Name  Ludic
  1  Age  29
  1  Profession  Tortured Soul

The key is not unique. There is no primary key. So to hunt down all the properties of User 1, you have to do a query for all the records whose Key is 1.

I think that doesn't happen in keyword-value stores. Your key 1 has to be unique: it retrieves one blob, and that's it. You have to stuff all the properties into that blob somehow: for instance, by treating it as an array of the keys of other blobs.

Derek could have used multiple tables. That still gives you all the flexibility. Just that if someone wants to invent a new property, they have to add a table.

Then we have

  Name table:       Age table:     Profession table:
  1 Ludic           1 29           1 Tortured Soul

The keys are unique: we fetch key 1 from each table, and we have the three properties. Not great compared to fetching one row with three fields, but better than stuffing everything as rows into one table.