Hi Andrew,

When we create product with product type "service",Procurement Method = "MTO" and Supplier Method="Manufacture", and we sale that service in OpenERP it will create task under project management. (You need to install project_mrp module to activate it). So the task created by procurement order will be assigned to Product manager as responsible person for that task, this is one purpose.

And it can be used as tag on product also.

Regards, Mustufa Rangwala