The greatest disadvantage of working with drop shippers is lack of control. Once you sell the product, they will take care of everything for you. At least, you hope so. Do your homework prior to committing to a drop shipper. Search online for reviews and comments about the company. Visit blogs and forums and try to find out as much as you can. It requires a lot of work to set up your site for a drop shipper. Make sure you only invest your time in a company that is reputable. If you run across a company nobody has ever heard of before look for another one. Let other resellers go through the growing pains with a new drop shipper. Check back with the company six months or a year later.
Your reputation rides on partnering with a drop shipper. You can only be as good as they are. If they have poor fulfillment, you have poor fulfillment. If they offer low quality products; slow service; inaccurate shipping; awful customer service, you will hear about it. Your customers have no idea that terrible shopping experience is not your fault. To them the drop shipper is invisible.
In addition to the lack of control, profit margins may be unattractive while working with a drop...