The number of bitcoin units is just a property of the number of decimal places that are used in each transaction. Bitcoin can actually be changed to support more in the future if needed.

This has no economic effects since you're just adding more ways to subdivide a dollar.

If you're looking for weaknesses, there's a list here:

https://en.bitcoin.it/wiki/Weaknesses

Deflation is more of an economic problem then subdivision; since it's very unlikely that can be changed.