By tagging a phone call as spam, users effectively block the caller's number from ringing their various phones or leaving e-mails. However, the marked calls will end up in a spam folder, which can be manually filtered at a later point.
Google Voice, released as a preview on March 11, allows a user to condense his or her various phone numbers into a single one, and provides other services such as automated voice mail transcription and GOOG-411 integration.
Google Voice is an updated version of GrandCentral, which Google acquired in July 2007.
The ability to block phone spam is an updated carryover from GrandCentral, with some added muscle provided by Google's ability to create databases.
"One of the lesser known features of the Phone Spam filter is that we also collect numbers from reported (and confirmed) Phone spammers to block them for the benefit of all our users," Vincent Paquet, a Google Voice product manager, wrote on the official Google Voice Blog. "These are not individual pranksters reported by individual users, but automated dialers that call thousands of numbers every day."
Paquet went on to claim that the Phone Spam is "blocking tens of thousands of calls on a daily basis, and that number is growing daily."
Despite this privacy feature integrated into Google Voice, Google has attracted the ire of privacy advocates by announcing new interest-based advertising, a brand of "behavioral targeting" that utilizes users' previous searches and page views to deliver targeted ads.
Other companies, such as Yahoo, have their own behavioral-targeting advertising models. However, Google seems to have attracted more controversy, perhaps because of its position as the No. 1 search engine; Google argues that it gives customers sufficient granular control over their privacy preferences.