Several piles in the game (in particular: development cards and building blocks) are limited. In a real game it is clear when the pile is (almost) empty. In Pioneers, this instead often comes as a surprise.
There should be a warning that is hard (or impossible) to miss when the pile gets to about 5 cards or pieces. For the build pieces, there is a counter on screen, but that is much less obvious than the real game.
Idea for how to do this:
The only other piles that can get empty are the resources in the bank. I think we already added something for that in the gold selection dialog. That's also the only place where it matters really.