It bears repeating that a statement capable of truth value cannot be fallacious. All too frequently truthful statements about a person are defended by resort to the ad hominem fallacy. The ad hominem fallacy is intended to defend against a string of qualitative statements, e.g., “he’s so evil you can’t believe anything he says” or the “so-called representative.”
However, calling out failing to disclose or purposely hiding a conflict of interest as astroturf, or otherwise pointing to specific facts that are capable of truth value is not an ad hominem in the normal sense of the term.
For example, when Judge Alsup demanded that Oracle and Google disclose any bloggers it had paid to write about the Oracle v. Google case, Judge Alsup was not engaging in an ad hominem attack on either party. Rather, he was requiring the litigants to disclose to the Court (and consequently to each other and to the public) what they had or had not done in a desire to shape the outcome of the case.
If you were to take Google’s version of that list (sometimes referred to on MTP as the “Google Shill List”) and say about someone listed on it “that person shills for Google, you can’t believe anything they say”, that would be an ad hominem attack. If, however, you were to say, “That person is on the Google Shill List” with a link to the court document, I would argue that is a factually correct statement and not ad hominem. And if you were to say, “That person is on the Google Shill List, therefore be careful about believing what they say as they may be shilling for Google again,” that would also be a factually correct statement and is not an ad hominem attack. You could substitute “Google Shill List” with “Google’s Response to Order to Supplement” and vice versa, but that is just editorial discretion and a link to the actual document allows the reader to see that document.
While it may make the person or organization about which it said uncomfortable, statements capable of truth value are qualitatively different than the “He is evil so don’t believe him”.
Likewise the sequential antidote fallacy. Continuing the Google Shill List example, when an organization on the Google Shill List takes a dozen unequivocal and irrevocable actions (such as filing amicus briefs in favor of Google or Google’s positions in court under oath) and then takes one or two actions against Google’s interest, the one or two actions should not be trotted out as disproving or as an antidote for the dozen other actions for which the organization was paid.