The e-commerce company's heavy spending won't last forever, but the growth it produces will.There's no denying that investors were less than thrilled with the third-quarter results MercadoLibre (MELI 4.76%) posted last week. Shares tumbled more than 16% on Thursday alone in response to the numbers, and are still well down from the pre-earnings peak at the time of this writing.For investors who can look past all the post-earnings noise, however, this pullback is a buying opportunity. The market's ignoring an ...