How would Google offer you this service if they didn't "collect" your data?
Well it won't be publicly searchable unless you decide to share it. One of the features is user-based access permissions.
But Google has access to it, which I think is vog's point.
Sure, I guess my point is, how would they use it?
It's not because you technically have access to something that you should or will access it, for a myriad of reasons.
> should
You need to read the contract/terms of service to determine what you are granting them with regards to your data. You might find that they want to keep an option open that you can't accept. You might also find that you are okay with what they propse. This is one of those times when you actually need to read the fine print.