Personally I have not experienced it, but I have heard of people scanning for LGPL library usage in iOS apps, then essentially extorting the developers for their source code.

I can't find the specific article now, but I am extremely careful to avoid anything GPL or LGPL.

It's unlikely to be a problem until an app is highly successful, but once that happens people will grasp at whatever straws they can, e.g. https://en.wikipedia.org/wiki/Google_LLC_v._Oracle_America%2....