Spam accounts for 83% of e-mail, according to some estimates

Jason Smathers, 24, faces charges of conspiracy after allegedly stealing the AOL customer list.

Prosecutors say the list was later used to send massive amounts of spam.

Mr Smathers and an alleged accomplice face a fine of at least $250,000 (�138,000) and a maximum jail sentence of five years.

Gambling service

The alleged accomplice, Sean Dunaway, has also been detained and charged with conspiracy.

Mr Smathers, who worked at AOL's offices in Dulles, Virginia, passed on the addresses to Mr Dunaway, 21, of Las Vegas, Nevada, according to prosecutors.

Mr Dunaway is alleged to have used the list to advertise an internet gambling operation and then sold it to other companies delivering spam.

Mr Smathers did not have permission to access the screen name list and used another staff member's access code last year to steal it, prosecutors said.

AOL has said it is reviewing its internal procedures in light of the arrests.

It is unclear how much money Mr Smathers is said to have got from selling the list, although prosecutors say Mr Dunaway paid him $100,000 for an updated version.

Spam now accounts for up to 83% of all e-mail, according to some estimates.

A movement to get rid of the nuisance e-mails is now under way in the US.

The arrests are thought to be two of the first prosecutions under new federal anti-spam laws.