The popups are coming

Here you have a row of 2-family 20x50 2 story houses. Identical to the landmarked ones on Lefferts ave or E 10th st, which now go for about $1.6m. 

Well, surprise surprise, we have no such landmarking here. So an enterprising developer has bought one of these row houses, and plans to double its height, right smack in the middle of the row of still-2-story neighbors. 

In Washington DC these are known as "pop-ups" or "middle fingers". 

 http://www.washingtonpost.com/local/2014/06/22/96a2222e-f307-11e3-9ebc-2ee6f81ed217_story.html

Could this happen throughout Flatbush? or is this an anomaly? 

BTW my house is very similar, with permissive zoning, so I could, in theory, put two more stories on mine as well.