If one researches the company's history, MongoDB came from a specific need the founders had for another product: ShopWiki.

ShopWiki is a shopping price listing site, where it keeps tracks of prices for any item: computer, clothing, food, etc. ShopWiki needs to be able to store, access, AND search amongst all of these different items. So, MongoDB is the perfect solution.

If the application being built has similar requirements to ShopWiki or a retail site where it sells _everything_, then MongoDB IS the right choice, because the founders basically built MongoDB for ShopWiki.

To sum it up: Is MongoDB the right choice? If the product is similar to ShopWiki, then yes.