Large Sharepoint document library integrated in MS CRM

In our MS CRM 3.0.project we have the need for integrating a Sharepoint document library in MS CRM 3.0 for storing the account correspondence. We have about 100.000 accounts and an average of 5 Word documents per client. Question is whether Sharepoint will perform sufficiently and if we will hit some built-in boundaries. According to this info the limit of the number of documents will not be a concern for now but performance is. Recommandation is to store the documents in a folder structure and not in a flat structure.

What would be the best practice ?

Options I can think of are:

1. One folder per client
2. a folder per letter of the alphabet
3. another option.

Somebody any additional ideas?