yes, it is.
first, it takes people off the site. are you clear on that? If they do not hit "cancel" it takes them off your site. As a developer, you NEVER want that to happen or allow someone else to have that kind of control over your traffic. Period.
Second, it is obtrusive and unneeded step to get past it. Do not care if it is just 1 click, it should not happen.
/** SGS3 (rooted & stock ROM) **/
/** Asus Prime TF201 (rooted & mildly OC'd) BRICKED BY THE ASUS OTA JB UPATE!**/
/** OG Droid (rooted & OC'd & all hacked up) **/