Hi WizzyWig,
The plan we're on with our ISP does not allow us to make money from the site in the form of advertising income, subscription fees, etc etc (donations are the only exception).
So if we were to run advertising, we would have to run 'a lot of it' as we'd be moved to a commercial plan and it costs a lot more.
Also, historically donations has proven more beneficial to OFPEC and the community (you guys don't have to put up with advertising), due to the generosity of this community and the fact that we only ever ask when we really need it.
Hope this helps clarify why we don't consider advertising as an option.