As others have pointed out, the gentrification of social networks echoes the gentrification of real life neighbourhoods too.
But it happens a lot quicker.
Notice that right now on Twitter, progressives are kicking up a fuss.
They don't want to leave.
This is their neighbourhood.
But they'll have to leave -- they don't own Twitter. They've always been renters. The only reason you were ever around was to make the place desirable.
And now you're being evicted!