Today I was playing minecraft on a flat world with structures on to test out my new 1.8 skin. I found a village in the world, but it only had one villager in it. It also had 2 blacksmiths, but no chests. I found a house with stone slabs in it, but only 3 / 4 was there. Then, there was a little 5x4 farmhouse. Only HALF of it.
Well, that can happen. Remember that snapshots are just test versions and in no way stable enough to become actual releases. Check if it has been submitted on the bug report. If not, submit it.
This actually has been happening for a long time now. It's an error, placing blocks or reloading the world fixes it.
Here are some screenshots:
Praise be to Spode.