Every fiduciary and every person who handles funds or property of an employee benefit plan must be bonded. In general, as a fiduciary you must be bonded up to 10% of the amount of the funds in the Plan up to a maximum of $500,000 (in most instances). This bond is required by the ERISA to help protect employees in the plan against losses to their plan due to any fraud or dishonesty.
It is very important that you as a plan fiduciary (therefore plan official) to look over the guidance related to these bonding requirements to make sure you have adequate bonding! You are ultimately responsible if something was to happen and the plan was not bonded. The US Department of Labor has issued Field Assistance Bulletin No. 2008-04 that has guidance regarding ERISA Fidelity bonding requirements. (http://www.dol.gov/ebsa/regs/fab2008-4.html)