I agree with some caveats. Whilst Steemit is already kind of a killer app - it would be even more effective if there was a marketplace where people could spend the money they earn. It could potentially create a true economy.
"Content creators, popular personalities and merchants can now promote and sell products and or services directly on the Steemit platform, user to user… NO MIDDLEMAN."
This is where the caveats come in. I think it would need to be done carefully though so as not to detract from the primary content sharing nature of Steemit and also to stop it turning into a shop front with people or businesses posting content that is of an advertorial nature.
Some strict rules would be required in order to control this. Perhaps also allowing people to hide (or switch off) marketplace functionality if they want to purely see standard content would help with that too.
If it could be done without detracting form everything else then it could be huge but it would need to be considered carefully so as not to damage the platform.
Right now the lack of ads and promotion is refreshing particularly when compared to the flood of such material we are bombarded with on other social media and content platforms. It is one of the main distinguishing features.
The potential is huge though if it could be done right.