I have written a few blogs recently on the subject of data scaffolding. Let me make a summary of them.

Data scaffolding is a technique to artificially create a data structure for the purpose of visualization. It will either reshape the original data or blend multiple data sources in such a way for better visualization.

The technique is pioneered by Tableau Zen Master Joe Mako.

The general methodology is as follows
1.Create a table of pure dimensions to act as the primary data source. It sets up the structure necessary for visualization.
2.Create measures from secondary data sources by blending.

There are two major use cases for scaffolding: Data Reshaping and Data Blending

Data Reshaping: single data source
The original data structure is altered through the scaffolding, such as unpivoted, for better computation or better visualization.

Scaffolding Video Lecture by Joe Mako
Data Reshaping via Scaffolding

Data Blending: multiple data sources
In the regular blending, there could be data loss in secondary data sources, because it's kind of like a left join.

In many cases, no one data source is more primary or secondary than the other sources. Thus we need a third party to act as the primary to all the actual data sources. This third party is a data scaffolding that is created artificially.

Blending Data Via Multi-Dimensional Scaffolding
Lossless Data Blending via Scaffolding
Blending Dates via Scaffolding

Examples of Scaffolding around the web:
Facebook Jeopardy: Create a Single Sheet Waterfall Chart in Tableau
GOOGLE ANALYTICS IN TABLEAU: BLENDING DATA FROM MULTIPLE ACCOUNTS
Basic Monte Carlo Simulations in Tableau