How common is it for someone to need a thyroidectomy?

Common. In this day & age where people are getting imaging studies more frequently, "incidental" thyroid nodules are found more easily, leading to more biopsy and more surgery. Approx 50, 000 new thyroid cancer cases are expected in 2011 resulting in approx 2000 deaths. The decision to proceed with surgery depends on discussion between you and your treating physicians (surgeon, pcp & endocrinologist).
Common. 10% of the adult population in the US has thyroid nodules. Many of them are found accidentally on ultrasounds and CT scans and MRIs. Not all of them require surgery, but it is a very common operation.