As far as I can tell, this is running from their servers - which means yes, you need to be able to trust the person who ultimately controls this at a bare minimum. Some trust him, some don't - some have good reasons, some don't.

I can evaluate this as it is, but if I was not trusting of a company, I can't then entrust my data to them, and so I can't evaluate a thing as any more than a toy.