It is completely your choice. That being said there are people that will come to your wedding that might not know you particularly well or at least your taste. As PP said you run the risk of duplicates and random things. Plus returning those things could be a headache without a registry.
I found a place to register that's a little less typical, with places to pin items from all over the internet, you can link to current registries and even add a honeymoon fund! Seems like a one stop shop, not to mention it's easy for your guests to navigate all of your registries. Check out my blog for more details