Here you go (did the ACORN workers have a reasonable expectation of privacy at their place of business to conspire and assist in criminal activity (while probably using public funding)?):

Under Maryland's Wiretapping and Electronic Surveillance Act, it is unlawful to tape record a conversation without the permission of all the parties. See Bodoy v. North Arundel Hosp., 945 F.Supp. 890 (D. Md. 1996). Additionally, recording with criminal or tortuous purpose is illegal, regardless of consent. Md. Code Ann., Cts. & Jud. Proc. § 10-402.

Disclosing the contents of intercepted communications with reason to know they were obtained unlawfully is a crime as well.

Violations of the law are felonies punishable by imprisonment for not more than five years and a fine of not more than $10,000. Civil liability for violations can include the greater of actual damages, $100 a day for each day of violation or $1,000, along with punitive damages, attorney fees and litigation costs. To recover civil damages, however, a plaintiff must prove that the defendant knew it was illegal to tape the communication without consent from all participants. MD. Code Ann., Cts. & Jud. Proc. § 10-410.

State courts have interpreted the laws to protect communications only when the parties have a reasonable expectation of privacy, and thus, where a person in a private apartment was speaking so loudly that residents of an adjoining apartment could hear without any sound enhancing device, recording without the speaker's consent did not violate the wiretapping law. Malpas v. Maryland, 695 A.2d 588 (Md. Ct. Spec. App. 1997); see also Benford v. American Broadcasting Co., 649 F. Supp. 9 (D. Md. 1986) (salesman's presentation in stranger's home not assumed to carry expectation of privacy).

http://www.rcfp.org/taping/states/maryland.html