Silvery - 9:07 pm on Mar 22, 2010 (gmt 0)
ken_b, my point is/was that for most top SEO agencies, full disclosure is absolutely not possible, due to nondisclosure clauses required by many clients. The idea that these companies should break their contractual agreements in order to satisfy one's curiosity is not at all realistic.
Further, it's simply inadvisable. For instance, I've had past clients who insisted upon doing some things that are directly against Google's guidelines, despite my strongly-worded advice otherwise. If Google knows all of my clients, is it not possible that they might choose to penalize all of my clients due to something bone-headed that one of them does, based on a false assumption that I could be the cause of black-hat behavior? Oh, absolutely.
Just for comparison's sake, IBM does business with a great many companies, but likely only discloses a choice few. It's not necessary for them to disclose every single last company they do business with in order for someone to assess whether they're credible/trustworthy or not. In a like manner, many top SEO firms rely upon publicizing only a choice few clients, or they rely upon word-of-mouth endorsements. It's not necessary to disclose everything in order to make a reputation assessment.
An SEO agency that publicizes every single client for whom they do work is an SEO agency that does not use very sophisticated methodologies, most likely.
Simple due diligence in choosing a company should work well in many cases. Who is behind the company? I wouldn't choose a firm that doesn't list out the names of some of its top personnel. What are the reputations of the personnel at the firm? Who have they worked for previously? Who has endorsed them? What do they say in their blog posts, and do others quote them? Do they speak consistently at recognized industry conferences? Etc.