Without going into the details of how this could be done, I would like to point out some reasons why we should want this:
1. Vendor lock-out:
In spite of the open standards that are supported by enterprise technology vendors (such as Oracle and IBM), the vendors are usually after a package deal and want you (the consuming enterprise) to become dependent on them. In other words: a vendor lock-in. A more open commerce model for enterprise technology (being able to literally buy them off the shelf) helps to prevent that.
I would like to be able to compare comparative technologies from different vendors by specifications, total cost of ownership, installed base, et cetera. Such information should become a lot more transparent than it is today. Also, enterprise technologies are often hard to compare because of the way they are assembled. Often they consist of a suite of integrated technologies that you could probably pick separately but won't easily mix (requiring much extra customization) together with technologies you already have but from other vendors.
3. Enterprise level folksonomy
Selecting a new enterprise technology is often an expensive affair in itself. Many man months are spent on product selection. What if a lot of that time could be saved? I find that I would like to be able to call my competitors in the market and asked them what enterprise technologies they are using and why they chose it. Yes, we could use an enterprise community that is divided into markets and sectors where we can share our experiences with enterprise technologies and vendors. Your decision to purchase an enterprise technology could be based more on experiences that other enterprises have shared rather than the subjective advice you will get from the vendor.
I know I am probably overlooking a lot of important details, and make this look overly simple but we should at least be able to implement no. 3. Let me know what you think!