<p>I was wondering about the best practices regarding this?  I know there are two ways to use IIS and host multiple websites. </p>

<p>The first is to have an IP for every website </p>

<p>The second is to use host headers, and a single IP Address for IIS</p>

<p>I was wondering which was the best practice, and why one should be preferred over the other?</p>

<p>Thanks!</p>

I personally separate sites based on the relation to each other.  For example all of my business sites share a single IP adddress (1 domain currently).  All of my personal/community sites share a second IP address.
The differences can come over time when it comes to sending e-mail as I know that IP comes into play in some blacklisting systems, so if one site with a shared IP address causes problems it CAN cause issues for the other sites using that IP.
I am sure there are other items, reasons, and justifications, but those are at least mine...