Well, I think it's a definate must to be more demanding when it comes to dedicated IPs, especially with the increased level of spam, phishing, etc.

Dedicated IPs open quite a few doors for online criminals. For this reason alone, I think increased demand for justification is...well....justified.

Keep in mind however, that I have never had an instance, or even heard of one, in which an allotment of IPs were denied by a datacenter or ARIN.

Dedicated IPs do come into play however, when it comes to spam and blacklisting. For example, some blacklists don't stop at the mail server. They also dig info on the sending domain to retrieve the IP of the domain sending the mail. They then blacklist the IP, and in most cases, the domain too.