Now what happens if other sites and apps do the same? Will our address books change every day and contacts fill up with dozens of unused email addresses? Many o

Now what happens if other sites and apps do the same? Will our address books change every day and contacts fill up with dozens of unused email addresses? Many of Facebook's growth techniques have been imitated by other startups so going into the territory of manipulating data that has always been off-limits is a big step. If another social site uses those techniques against to manipulate data on Facebook profiles, will Facebook change it's mind?