Big data and data mining for CRM?
The two modules where you can really harness data mining and big data techniques are probably Leads and Opportunities. The reason is that, as you've written yourself, both contain 'potential' information that you can harness (through predictive algorithms) to get more customers. Taking Leads as an example, you can use a variety of machine learning algorithms to assign a probability to each account, based on that account's potential for becoming your customer in the near future. Since you already have an Accounts module which gives you information about your current customers, you can use this information to train your machine learning algorithms. This is all at a very high level but hopefully, you're getting the gist of what I'm saying.