I believe certification of technical communicators is unavoidable, given the current status of related professions and our technological environment. Either the STC develops a certification program, or someone else will do it.
The virtues of certification cannot be ignored, but they are outweighed by the drawbacks: There’s no evidence that employers will value certification; it can be highly subjective; and it requires ongoing renewal, even for experienced practitioners, to avoid diluting its value. The more important task must be to demonstrate our value to employers. Only once they understand our value will certification provide a means to assure employers that they can expect to receive that value.