Scallop is a simple delicacy compared to the other more exotic seashell options. You will expect them often in a sushi restaurant. I think scallop only taste good when served raw and it loses a great deal of its taste when cooked. You can taste the Unami (rumoured 5th sense of taste, representing freshness, just like eating MSG) of the scallop when it is served fresh. And it tastes very good in that way.
You should look for sushi grade scallop. In the US the sushi grade scallops are flash frozen and thawed before it is consumed as an attempt to kill all the parasites in the seafood. Usually it should do the job, but you can avoid eating them. For I would take the risk in order to enjoy sushi properly. If you avoid sushi, you should avoid oyster in the first place. There are TONS of bacteria in oyster because of the nature of how it thrives. Raw oyster contains the highes amount of hepatitus bacteria and just the sheer thought of it makes me sick. Nowadays I don't eat oyster raw (or just one) but I eat sushi without any problem. My motto is cooked food can be contaminated also, so it is not the food but the chef that prepares the food.
Unfortunately flash frozen sushi will usually tarnish the taste and texture of sushi fish, but recently it is required by the FDA that all fishes (except tuna!! must be because of the expensive otoro) has to be flash frozen. So go to Japan or elsewhere if you want to try the 100% fresh scallop.