That goes into notions Selkirk has raised before about central config files. It doesn't have to be that way. A (possibly non ideal) solution would be to have a file along side every page controller which contain info about what filters should run as well as anything the filter need e.g.;
I guess it would be nice to be able to define general, always used filters in a config file, registry, whatever, but then be able to add other filters as required on a per page basis. I don't immediately see an easy way to deal w/ the ordering of the filters tho, plus maybe the config file parsing would slow things down too much?