The actual rules are very difficult to read, and are very complex, but they boil down to simplicity in unsophisticated transactions.
If you purchase more than 5%, you filed 13D or 13G. You file another when you fall under 5%.
If you hold more than 10%, or are an officer or director, you file Form 4 on every transaction except those involving less than $10,000 stock value. You stop filing Form 4 if you step down, or fall under 10% and are not an officer/director.
All directors and officers are supposed to file an annual Form 5 unless all transactions were reported on Form 4.
If the SEC was enforcing this on the pink sheets, there would be a lot more filings to read, and small investors would be better protected.
With the Sarbanes/Oxley modifications, you should be able to view the holdings of every director or officer of a company within 48 hours after any transaction involving $10,000 or more.