Even though very interesting, the main article had been even more useful if that had been clearly defined.

The paper uses these definitions:

Products company

"... the majority of a firm's revenues come through sales of standard offerings." 1)

"Product companies ... generally want to sell as many copies as they can of their product as is – that is, without adding special changes such as one-of-a-kind features for individual customers. 2)

Services company

"If firms go in this direction of providing more customized features, services, and maintenance than they do standardized products, then the more people the company is likely to need, the more unique projects or labor-intensive work it will probably undertake, and the more the firm leans toward becoming what I will call, for short, a services company."3)

It is interesting to note that some of the things the paper defines as "products", like products created by Microsoft, Adobe and Intuit, now in many cases can run as a service on the web.

Is it then still a product, or has it changed to a hybrid or a service?

Sources, all from: http://ebusiness.mit.edu/research/papers/197_Cusumano_ProdSr... 1) Page 3 in the pdf, 2) and 3) Page 4 in the pdf.