W3.do short links are 301 redirect. 
No surprises to redirect you to site you don’t expect, as even those “links previews” can show up the actual site’s meta data. 
Like all links on internet, it’s user responsibility to keep themselves safe. 

 I concur, the user bears the ultimate responsibility. By the way it's not something specific to your service. I really think you have done a great job. If used with responsibility it can be a great tool. 

 Yup