i have heard that Memphis has been de-annexing
A few years ago, Tennessee almost passed legislation that would have allowed folks in recently annexed areas to sue to essentially secede from the annexing city, brought about by residents who were dissatisfied with city taxes and inconsistent expansion of city services to the new areas.
As part of the debate on the bill, Memphis agreed to study de-annexing areas where the cost of expanding full city services didn't make sense in light of the tax revenues collected.
Here's a map of the deannexed areas.

I can't quickly find the complete estimates of impacted population, but the population decline of Memphis proper since 2010 is probably a combination of migration and deannexation. (I think the impacted areas were between 1% and 2% of the city, population-wise.)