If you plan to run draft (tap) lines from a keg in a refrigerator to a tap some distance from the refrigerator, for example to a bar, you are likely to run into issues with foamy beer.
If foamy beer is an issue for you, the cause is likely due to beer warming up in your draft lines. As the temperature of your beer increases, CO2 naturally wants to come out of suspension, resulting in foamy flat beer....Boo. So in short, if you keep the beer cold, you will keep the CO2 where it belongs in your beer not on top of your beer (foamy head). Wrapping your tap lines in foam insulation is a great way to help keep your beer cool once it leaves the refrigerator. Again if you keep the beer cold, CO2 is more likely to stay in suspension, and less likely to cause foam.