Hi @EmilyCowan ,
The Only downside i think is managing the Inventory synced across all the channels but softwares like webgility Unify or any other apps are managing pretty well. Other downside is always the fees associated on selling on these platforms. So Lets take an example i can sell a product on my website which will cost 20$ to a customer but on Amazon or eBay i have to make sure they are priced correctly so i can compete with Other sellers and also can make money on the sale.Hence all the cost benefit analysis needs to be done prior to listing on Marketplaces where competetion is waiting.
