I am planning for my own startup and I am kind of skeptical towards hosting and cloud.
I always wonder what if my app becomes popular and valuable.
The server owner will have access to my database and at least the binary of my app. I am exposed to a risk that the owner have a copy of my asset.
Pick a reputable vendor for your host and cloud.
I'm personally not a fan of cloud computing. You give up too much control and unless you're paying a lot of money you have no control over downtime, etc.
If you're still worried about security you can get your own boxes and put them in a co-location facility, but then you have to worry about administration / security yourself.