I have noticed that 9 out of 10 shared hosting packages offer static IP. Even my dedicate provider. But the funny thing is I found it is pretty diffult to request IPs from my upstream provider. They told me "all IP addresses must be justified and 80% utilized before new IP's are issued".

Exactly how to you justified the usage. Lets face it, people expect to get static IP. But this does not mean that they will use anonymous ftp access. In fact, I dont think more than 10% of my clients is actually using anony FTP access.

One other problem with shared IP hosting. It is very diffult to check the actual bandwidth usage. Especially with FTP traffic, which can make a huge difference. How do those providers know exactly how much bandwidth are those shared hosting clients using??

well, what they mean is simple, show that you are using 80% of the ips for hosting accounts...

otherwise anyone will go around buying blocks.. and dominate the market :)

The problem is I cant force my clients to use anonymous ftp.
So I am just wondering how do other hosts deal with this problem? Also, exactly how do they check to see if IP is justified under Arin's policy..

More hosts will verify the ip is 'live' through a ping test. But, that doesn't really answer your question.

Who is the actual owner of the IP block (registered under name of hoster2) that is purchased from ARIN ?

The hoster or the hoster(hoster2) from the hoster? ;-)

This is COMPRESSED a lot. I hope someone understands what I mean. If not I will explain myself better.