Woody,
In my experience, I have found that if the dough formulation calls for small amounts of yeast, it doesn't really matter all that much whether the lid on the container is tight fitting or not. However, for larger amounts of yeast where the dough expands a lot, I think it is a good idea to allow a way for the gases to be released during fermentation while maintaining the moisture. So, what I do is to drill a small hole in the middle of the lid.
Peter