Micro-blogging site Twitter's admittance this week that they used to copy and store the entire address book of smartphone users is causing quite a stir. The company has tendered an apology and has indicated that it will update it's privacy policy. But is that enough?

We want to be clear and transparent in our communications with users. Along those lines, in our next app updates, which are coming soon, we are updating the language associated with Find Friends - to be more explicit, Twitter spokeswoman Carolyn Penner said to The Los Angeles Times. According to the report, Twitter used to store contacts in iPhone for a period of 18 months.

It turned out that whenever smartphone users clicked the button for 'find friends' feature, the entire address book used to get copied and downloaded to Twitter Server.

The controversy over leaking out personal information by SNS erupted when Arun Thampi, a Singapore-based app developer discovered that his contacts got copied without his permission by a new social network called 'Path'.

Technology bloggers soon discovered that iPhone apps like Facebook, Twitter, Foursquare and Foodspotting similarly uploaded user data - without permission, in some cases, Daily Mail reported.

Only after pressure from U.S. legislators who asked why Apple has allowed such practices on its phone, the tech giant has made an effort to improve its guidelines over privacy.

On Wednesday Apple announced a change in iOS-based apps guidelines that requires the app to ask 'explicit permission' from smartphone users before collecting and storing personal information and contacts data.

Apps that collect or transmit a user's contact data without their prior permission are in violation of our guidelines, an Apple spokesman told Reuters. We're working to make this even better for our customers, and as we have done with location services, any app wishing to access contact data will require explicit user approval in a future software release.

Meanwhile, Twitter users have expressed concerns over the privacy issue and some of them are wondering whether Android-based apps might have also allowed their personal information to leak out in a similar way.