This is an educated guess, but maybe the SEC received a complaint about Bitzio earlier than the date that I filed my complaint about Greenshift. FWIW, I never bought Bitzio stock, and I never filed a complaint against them, but anyone who did own their stock could've filed the same online complaint that I did about Greenshift.
Judicial ethics sometimes prohibit a judge from making a motion in a case that he is presiding over, even if he knows that the motion would succeed in his courtroom and in an appeals court. All he can do is to ask one of the lawyers if he wishes to make a motion. That suggestive language is not a violation of the judge's ethics rules.
Likewise, the SEC may not have the authority to screen all of the thousands of registered and publicly-traded companies to find out if any of them are delinquent in one or more filings. They may have to wait until a complaint is filed.
I filed a complaint against Greenshift last spring. If that was the first complaint against them, then perhaps the SEC's limited manpower and budget has resulted in no visible enforcement action being taken so far.
I have two answers for you. First, an exercise like that would be a labor of love, because of the thousands of registered companies who are required to file reports. I'm not an attorney, so my second answer is another educated guess. Maybe the only people who can trigger an investigation of a corporation by the SEC are people who are shareholders of the corporation.