I never thought about such an step by myself, maybe as I never encountered such a thing upto date.
But if you run your own Webspace you should never steal any ones content or bandwidth. Then as soon as he notice it you can get some real problems, maybe he starts a lawsuite against yours(you maybe ignored some copyright laws, you caused some additional costs for him(bandwidth)). What does happen if he simply replaces the content/redirects your website to something which does harm your visitors, or does blame you?
On the Following WordPress Topic you’ll can read that someone linked to some JS of Website_A. This JS is the Output of some public free available WP Plugin, the JS code even mentions that it’s generated by some Plugin. But somehow the owner of Website_B was too lazy, or wanted to save some bandwidth that he simply linked to this JS file, on Website_A.
After the owner of Website_A recognized that someone was stealing his Bandwidth he created some mod_Rewrite Rule which redirected the Request from this JS to some other JS file, which contained an alertbox which appeared in front of the Visitor and told him that this Website steals some Traffic from another one. After one month the owner of Website_B discovered that JS change and removed the JS.
But it’s important to say that theoretically the owner of Website_A could have written any JS code into that file. So he could steal some Cookies of the Users of Website_B or anything else he would like, he could even start some Phishing attack.
The owner of Website_B made his website vulnerable because he was to lazy to get the script itself.
Every good Webmaster/Site owner does not steal any content, as this is unethical and maybe more important dangerous!