One time per person. http://www.rumoristrue.com/lgrumor/default.aspx

Sweepstakes Prizes:

Grand Prize: A high-end travel, lodgings, and entertainment package for up to six people, with the difference between the trip and $100,000 awarded in cash, OR a check for $100,000.
1st Prizes (25): An LG 50-inch plasma TV. (ARV: $1,400)

Additional Comments:

Alternate entry by text message and mail. Entry limits are only explicitly stated for the mail-in porton, but those state one entry per person.