Learning Spanish With Duolingo Can Be More Effective Than College Or Rosetta (techcrunch.com)

This feels like a commercial.

sounds like a commercial and i find these sponsored studies suspicious but I didn't know about the site before and it looks interesting.

The first problem is in the second sentence of the report: "The study lasted for approximately eight weeks."

Based on my limited knowledge of outcomes assessment and the current scholarship of teaching and learning, eight weeks is not a long enough period of time to meaningfully measure the effectiveness if any learning method (at minimum, you want retention data past the learning phase, i.e. it matters less how you score on a final exam at the end of a class than how you score on the same exam 1/2, 1, 3, and 5 years later, etc.)