Capacity concern - Problem or RFC?

This started out as a tweet:

ITIL question: if you have a Capacity concern on a system where you have a projected bottleneck, do you raise it as a Problem or an RFC?

So, an Incident is defined by ITIL v3 as a variance from normal service, or the failure of a Configuration Item that reduces Availability, and a Problem is the cause of one or more incidents. But what happens if you detect a Capacity bottleneck that has not yet caused an Incident, but which you anticipate in future would cause one if usage grows as projected and nothing is done about it?

Surely it cannot strictly be a Problem, because an Incident has not yet occurred. Furthermore, in some situations, calling it a Problem might have some financial implications, implying that the service was not designed or implemented correctly; that would be unfair if the service was designed as optimal for a certain user load, and it so just happens that user load has increased since that time. If calling it a Problem is going to lead to financial penalties, wouldn't this end up incentivising people to bury their heads in the sand? That wouldn't be a good thing.

But from a technical standpoint, treating it as a Problem is attractive. It may well be treated in a similar way to a Problem: the same technicians may work on it, the same processes of design and transition may be employed to address the bottleneck. This is a point made well by Stephen Mann when we were discussing this on Twitter. Do we call it a potential future problem? James Finister described this as Proactive Problem Management.

Or should we treat it as an RFC? Stuart Knipe raised some good points regarding the differences between RFC's and Problems. Problems seem to imply starting from some root cause analysis, whereas RFC's seem to start from business cases and requirements specification. But would it be right to be more business-like with a bottleneck that has not caused an Incident yet, than one that has?

Ruth Arnold points us in the right direction, albeit one that may not be conclusive, when she points at the Capacity Management Process. It depends on your local policy. Capacity Management produces many outputs, including metrics and monitoring, plans and projections, but when it also produces a to-do list of capacity concerns, how do you treat them: as RFCs or as future Problems?

As far as I'm aware ITIL does not specify how these concerns should be managed, so I guess it's up to you.

Please let me know...