I recently met a Swiss women who worked for a NGO involved with relief and reconstruction efforts after major natural disasters in places like Sri Lanka and Haiti. Because of her frequent travel schedule she couldn’t part with her passport for the time often required to obtain travel visas for future trips. Her solution: two Swiss passports. She uses one passport to travel while the second is being processed for visas.
Travel Tip: If plan to visit countries that aren’t on friendly political terms (think Israel and other middle east countries), places your home country may not allow (Cuba), or China after Tibet (since China often cancels its visa if a traveler visits Tibet first), having two passports that you can switch around will make border crossings much easier.
US passport holders can find more information on obtaining a second passport on the state.gov website.