Bought a lot of things over internet for years, including watches, computers, cameras etc. New and used. Never had any problem.
If you are a first time buyer, stay with trustworthy websites first: Amazon, Future Shop, Costco, eBay. With eBay, choose buys that have good ratings.
Bought a watch 6 days ago from Amazon but was not happy with the watch. Returned it and the postage was paid by Amazon. Pretty painless.