I see OCP as a benefit, if it is adopted by mainstream server vendors
For a few reasons:
1. The fundamental idea can scale. It doesn't have to be just for large rack-by-rack server farms. A single 1U or tower server enclosure could support the same interfaces to support components from different manufacturers.
2. Cheaper cloud services. I fully agree with the comments about smaller companies using more cloud/PAAS/VPS services these days, instead of running their own hardware, and OCP could decrease the cost of these services.
3. Per-server hardware cost. If I own a server from HP/IBM/Dell/Apple then I need to buy all the components from them. We all know that it costs more to by an HP 8GB RAM module than it would if I bought it from another vendor, and this could break that requirement. Support/warranty would become an issue, obviously, but that's where IT service companies have an opportunity to support an approved list of vendor-compatible parts.
4. I think that an important idea is that I can upgrade RAM and CPUs every 2 years, while running the same HDDs and power supplies for 5 years. These days I am more likely to have to buy whole new servers every few years, which costs more and produces more e-waste. This could be a major cost benefit to any scale of operation.
Of course, all of this requires adequate commitment from the major server vendors. If it stays in the ODM space then it will only be available to the Facebooks, Googles, Amazons and Rackspaces. But then again, we could usher in a new era of server integrators that make products available to smaller businesses, with IT services companies to support them. This could be a real opportunity.