No. If it is just a link with no explanation then it is blatant spam being used to help their own site. Even if the link is related they are not adding to your article at all, only promoting theirs.
Also mark it as spam before deleting so that your account will recognize that user as a spammer. Otherwise you are setting yourself up for for more of these types of spam comments by that user.
If they leave a comment with the link then it is up to you if you want to leave it up or not. I will usually delete them unless they are from a fellow hubber or take you to a safe website.
Norton has a site safety checker you can use for free.