We're in the same position that your current bank is in when it comes to fraud and theft: we're insured for it, and we follow industry-standard practices when something bad happens.
Most likely, what would happen is:
1. You realize that your account has been compromised. 2. You call us up. 3. We investigate your claims with our partners. 4. You get reimbursed. 5. If there was a security flaw on our side that we can fix to prevent this from happening in the future, we do so.
We have a comprehensive security review process and participate in internal and external (third-party) security audits. We're also taking steps to make it more difficult for attackers to compromise your account through multi-factor authentication and other mechanisms.
If you have any other questions about our security practices, please contact us: hello@simple.com or security@simple.com.