Starwood is generously offering 100 bonus Starpoints to SPG members (including those with an SPG Amex card) in exchange for a pledge to observe Earth Hour this year.

Register for your bonus at spg.com/earthhour and commit to switch off your lights for one full hour on Saturday, March 26, 2011 from 8:30 to 9:30pm local time. Your Starpoints will be credited to your account no later than April 15, 2011. For more information on Earth Hour, see earthhour.org.