The issue of differentiating between personalisation and customisation online is one I've experienced in discussion with a number of organisations.
The first problem lies with semantics - i.e. the definition of personalisation vs customisation with respect to the use and design of websites. I see one as automatic audience targeting (personalisation) and the other as the ability for the customer to manipulate the website to fit their needs (customisation).
As a business your first priority is to define your understanding of what each one means so that all parties are working from the same standpoint.
In terms of personalisation as per the above definition then, I believe this is the future of customer focused business intelligence. It is about understanding the customer, either as part of a larger group or as an individual and then presenting them with their own unique customer experience. In the next posts I'll explore how you can implement these and some possible avenues of ROI.