Virginia Business has an excellent article by Collin Hite on the uselessness of certificates of insurance. I wholeheartedly agree with his analysis.
The article discusses a new law in Virginia that attempts to prevent certificates of insurance from containing misleading language about what rights the certificate gives a certificate-holder. While that may be occasionally helpful, in my view the real problem with certificates of insurance is that they exist at all. As they cannot be used as proof of coverage, why issue them? The safer practice would be for an entity seeking proof that it is an additional insured on someone else's policy to require that the primary insured provide a copy of the coverage selection page. If the coverage selection page does not list additional insureds by name, that part of the policy that does name or define additional insureds should be provided. Although that won't prevent the problem of a policy being canceled by the primary insured without notice to the additional insured, it would be a step in the right direction.