Here's a simple test to determine whether you have built a truly scalable customer acquisition process: if you could choose to add an additional unit of sales or marketing resources, are you confident that the investment would generate an at least proportional growth in revenue?
The problem with most sales and marketing processes is that organisations do not understand where the most significant underlying constraints are. Until and unless they do, there's always the risk that they will throw resources at something that is not going to really influence revenue growth.
Some of these constraints are inevitably specific to the organisation and to the current moment in time. But there are a handful of common processes that always have to be understood and mastered before a truly scalable, repeatable and predictable customer acquisition system can be established.