I'm making a mobile app similar in functionality with Whatsapp where the user will have to select and contact acquaintances (friends, family, co-workers ..you name it) so I'm just wondering if it's bad to use a social source (faecbook) to pull friends instead of using the phone numbers the user has saved in the phone and make entries from that list.
Do you see any loss or gain in using Facebook to pull acquaintances instead of phone numbers? I would prefer going this route since it's much easier and involves less trouble with international phone codes or people in roaming etc.
One thing that comes to mind is that a phone contact list tends to always be more complete compared to social media but that really differs...I don't know! What's your opinion on this?
EDIT: It's not a messaging application but it uses someone's contacts to perform it's job though