So on my android phone i have enabled sync contacts as its handy to open the contact list on phone select a contact and go straight to there profile page but i notice that all of a sudden people who are not my friends on facebook but who are in my contacts (like work colleagues) are now showing as suggested friends in facebook, i can only assume facebook when syncing contacts uploads contacts to check against who I am and am not friends with.

Anybody else noticed this?

Most of the Social Apps do this.

LINE, for instance, does it every time you start the App to build your 'Friends' list, looking for phone numbers in your contacts database that match their authenticated user list.

I haven't done any research to see exactly 'what' they upload. Just the numbers, or other data as well.

And what happens to the data on their servers once it's been compared?

Your data tables have been scanned, citizen. And your number is up.

one of my client requested my presence on 'WeChat', since his team is all there for instant messaging.

in the registration, my 'native name', telephone number, email addresses been matched in their database and been propagated to anyone who has my name in their address book. WORST, it is NOT a 'suggested friend' but the app connected them automatically by default.

in 2 minutes, I got almost a hundred 'friends' and some far-reaching 'friends' even they didn't know I am here in LOS.

avoid WeChat !!