But I wouldn't worry about Carbonite or GoToMyPC. Both advertise in my newsletters. I've researched their security.
Let's start with Carbonite. Hackers could get to the data you store on Carbonite. But that would likely be the result of user error. It's the same type of risk you face with any service.
For example, you could disclose your password to someone. Or, your machine could become infected with keylogging software. If your password isn't safe, neither is your data.
But Carbonite has done plenty to ensure the security of the data it stores. Your data is encrypted on your machine with 448-bit Blowfish encryption.
Blowfish encryption has not effectively been cracked. Also, 448-bit encryption is very, very strong.