In the aftermath of 9/11, USCIS now conducts International Border Inspection System (IBIS) checks on each beneficiary of every petition immediately after the petition is logged in the mailroom. It may well repeat those checks before issuing the I-797 approval notice. On occasion, USCIS may also conduct a similar check on the individual signing the petition. Including the passport biographical data page enables USCIS to operate more efficiently.
In addition to the IBIS checks, USCIS appears in some cases to be running additional organized crime-related checks. When USCIS encounters the occasional "hit," meaning only that there is adverse information somewhere in the system, the result can be unexplained (often interminable) delays. In such cases, USCIS generally sends a Request for Evidence or other notice to the petitioner cryptically stating that the identified beneficiaries may be subject to additional processing delays, and that the petitioner may wish to authorize USCIS to drop the beneficiaries from the petition. In ALL such cases, the petitioner must recognize that failure to drop the beneficiaries at issue will, at least for the foreseeable future, stop adjudication of the petition in question in its tracks. In short, if you encounter this situation, drop the beneficiaries or face interminable delay.