Some hosts offer unique IP as additional feature for hosting.
What is it for? Why I might need it? I have read on search engine forums that if anyone wants to be succesful in search engines he
should have unique IP? Could anyone tell me what is it for?

In the end, the only cases where a unique IP is absolutely required for a site are if that site needs anonymous FTP or a secure certificate associated with it. Other than that, it's unlikely that unique versus shared IP sites will see any differences in other areas, including search engine rankings. There's the minimal risk that a shared IP might wind up in the blackhole list if a spammer operates off that IP - and then all the sites on that IP will be blocked as well. However, I think that's a rarity.

Annette is correct. If you do not need anonymous FTP or SSL. Then you dont need a unique IP. In fact, using name-based(shared IP) hosting speeds the servers up since it doesn't have to allocate resources for additional IP addresses.

But to get your money's worth, you should get a unique IP for your site :)

Now after all the good advice this person was getting, why on Earth would you say that? It seems to indicate that you are saying he/she *wouldn't* be getting their money's worth if they were not given a dedicated IP. A $15 package is only worth $10 if it doesn't come with an IP? :D

Thank you very much for all the advices.