No metrics are perfect, this is a good one I think for trying to get at developer mindshare. Actual API usage (number of calls) I think is not useful at all.

No metrics are perfect, this is a good one I think for trying to get at developer mindshare. Actual API usage (number of calls) I think is not useful at all. If heavy volume is concentrated in a declining number of apps using the Facebook API (just an example, I don't know) I think API usage can go up while mindshare is dropping.