Why is it against the law to put something in someone's mailbox?

18 U.S.C. 1725 states: "Whoever knowingly and willfully deposits any mailable matter such as statements of accounts, circulars, sale bills, or other like matter, on which no postage has been paid, in any letter box established, approved, or accepted by the Postal Service for the receipt or delivery of mail matter on any mail route with intent to avoid payment of lawful postage thereon, shall for each such offense be fined under this title" "TITLE 18 > PART I > CHAPTER 83 > Sec. 1725" Legal Information Institute google.com/answers/threadview?id=288629">http://answers.google.com/answers/threadview?id=288629 It appears that violation of this provision is an infraction, carrying a fine of not more than $5,000 for an individual, or not more than $10,000 for an organization. "TITLE 18 > PART II > CHAPTER 227 > SUBCHAPTER A > Sec. 3559" [defining "infraction" in subsection (a)(9)] Legal Information Institute http://www4.law.cornell.edu/uscode/18/3559.html "TITLE 18 > PART II > CHAPTER 227 > SUBCHAPTER C > Sec. 3571" [establishing fines for an infraction in subsections (b)(7) and (c)(7)] Legal Information Institute http://www4.law.cornell.edu/uscode/18/3571.html See also: "Domestic Mail Manual - D041 Customer Mail Receptacles" [especially section 1.3] United States Postal Service http://pe.usps.gov/cpim/ftp/manuals/dmm/D041.pdf