In a nutshell, you create a sync loop if you connect your devices and on-line services so that they form a closed loop. Sync loops are bad. On this page we explain the trouble loops can cause.
The extra short version: Do not make loops like in the picture below, set up your sources like this.
Syncing devices know pieces of information about their direct neighbors; Soocial knows which contacts are present on the Mac and on Gmail and it knows how to identify them. So do Gmail, the Mac and whatever is in that cloud. It is important to understand that all linked devices can only see their direct neighbors. In this example Soocial is totally oblivious to what is happening in the blue cloud. This is why we call this the big blue cloud of doubt.
Good question! It is not easy to explain this in one sentence. Please bear with us for a long story.
All contacts exisiting in the loop are interconnected. This means that if you would want to delete a contact in your Gmail (see the picture above) this would cause that contact to be deleted from Soocial, your Mac... and whatever is hidden in that cloud. The deletion of this contact propagates through the whole loop over the arrows. Follow the loop clockwise or counterclockwise, or alternate directions as you wish, at last one source will try to delete a contact that has already been deleted from that place. This is not a problem of course. So far so good...
But see what happens when a new contact is created. It is probably best illustrated with an example. Say you meet someone, at a conference or on a friday night at the bar, it doesn't matter. Anyhow, let's call her Anna. So you exchange phone numbers and then this scenario plays out:
To summarize: loops create duplicate contacts. Duplicates propagate through all sources filling up your whole address book in a very short time.
This is actually exactly what Soocial is doing. But it still doesn't solve all problems. Let us continue with the story:
The scary conclusion: if you delete a duplicate in a loop, you can cause the original to be deleted.
Luckily Soocial keeps a history of all your contacts, you will be able to retreive Anna's phone number. You can rely on it but it obviously is not a perfect solution. It is much better to prevent this situation alltogether.
Set up your devices and on line services so that they never close a loop. This is not just true for Soocial, it holds for all syncing solutions. One should always prevent making a loops. Note that if you sync your iPhone with a Mac and with Soocial you might already have created a small triangle. This is a slow loop since one doesn't continually sync one's iPhone but it will cause trouble nontheless.
Loops are bad, do not make loops, they are easy to avoid.