Yesterday the U.S. House Judiciary Committee, Subcommittee on Immigration, Border Security and Claims held a hearing entitled "Whether Attempted Implementation of the Senate Immigration Bill Will Result in an Administrative and National Security Nightmare."

Clearly they have an agenda, but they're also right. One of those testifying was Michael Cutler, a former INS agent. Full text at the link; a segment:

there are senators and others who insist on pushing forward to implement a guest worker amnesty program that would be utterly disastrous for national security... if this program were enacted, these millions of illegal aliens would be able to go to an immigration office, assume any identity they found convenient and receive official identity documents from our government. It would be a simple matter for a terrorist or criminal, to walk into such an office, provide a false name to the over-worked bureaucrat at USCIS who will probably be given only a minute or two at most to interview each applicant. The terrorist would then receive a guest-worker identity document in that new identity that would permit him to circumvent the various terrorist watch lists or so called, "No fly" lists and thereby embed himself in our country and gain access to what are supposed to be secure venues...

Another person testifying was Michael Maxwell, the former head of the USCIS' internal affairs division:

U.S. Citizenship and Immigration Services (USCIS) still isn't ready to handle a massive guest-worker program, even though President Bush and the Senate are pushing for one to be part of any immigration-enforcement bill, a former agency official will tell lawmakers today.

"An administrative and national-security nightmare already exists at USCIS," Michael Maxwell, who until this year ran the agency's internal affairs division, will testify, according to a copy of his prepared statement obtained by The Washington Times. "Implementation of the Senate bill would codify the nightmare and ensure that the criminals, terrorists and foreign intelligence operatives who have already gamed our immigration system are issued legal immigration documents and allowed to stay permanently..."