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"With orkut's new SMS feature, you can scrap your friends, look up their contact information and receive scrap notifications." Scrapping is a way of messaging another orkut user, by leaving a public comment.
Google also owns dodgeball, a mobile social network acquired in 2005, that informs users when their friends are nearby. The service is available only in the US, and it's not integrated with orkut, which is mostly popular in Brazil.