Gentrification is defined as the process of renovating and improving a house or district so that it conforms to middle-class taste.  Who is it that gets to decide what “middle-class taste” is?   And, from my perspective, many of the newly-built mansions represent something higher than middle class.  Regardless, it is the job of the city government to control the construction of these homes through its zoning, building and permitting departments.  I think the city could do a better job of assuring that the new structures conform with the existing appearance and character of the neighborhood, instead of allowing something that sticks out like a sore thumb.  There will always be gentrification and neighborhood improvement.  These just need to be controlled properly.