How do I find out what IP ranges a hosting company might put my site on if I sign up with them? I’d prefer some sort of tool that checks this – vs. asking the company itself. If any of their stuff is suspect in anyway, then odds are that they condone it and aren’t going to be honest with me when I ask.

I don’t do much emailing, but I do some (couple thousand/mo.) and I want to make sure the IP I’ll be hosting on isn’t on a RBL somewhere.

One of the commenters, Tom, made some good points in favour of dedicated IPs. And he is proven right.
Because it’s 2 years later, and BigG and BigY still haven’t taken any measures against Class-A, -B, -C IP SEO hosting.

I’ll give you some more reasons in favour of dedicated IPs :

Let’s assume that you have 5 websites all on a shared hosting account and one shared IP.

Scenario 1:
Your “neighbours” misbehave, spamming, phishing, warez, (illegal) porn.
You and your websites are living in the same “neighborhood” as far as BigG and BigY are concerned. They will ban the websites who are spamming, phishing, and have illegal porn.
Too bad for you they don’t ban on domain name. They ban on IP number, and IP range aaa.bbb.ccc.BAN.
So your websites are also banned. So you have to move, or go into negotiations with your hosting provider to bail you out with BigG and BigY.
Good luck.

Scenario 2:
Your “neighbours” are all perfect citizens. They are streaming paradise music, and wearing fig leaves, etc.
Problem is that your neighborhood (paradise) gets hacked.
Most webpages are injected with phishing code, spamming code.
Your websites are turned into bots.
Again, BigG and BigY will ban on IP number, and IP range aaa.bbb.ccc.BAN.
Even if the hackers skipped your pages, because you had all the latest script updates installed and had tightened security with the perfect .htaccess file.

Your websites will also be banned.
Don’t believe me ?
Go ask previous customers of IX Web Hosting.
Search BigG WITH quotes, for “IX Web Hosting hacked”.
Here are just a couple of them :
http://safebrowsing.clients.google.com/safebrowsing/diagnostic?&site=AS:32392
http://www.google.com/support/forum/p/Webmasters/thread?tid=2a2324104942560e&hl=en

Scenario 3:
Your shared server has a request queue. That single request queue is shared by all “neighbours”.
A couple of your neighbours are overloading the request queue.
Too bad for you that BigY and or BigY are just paying you a visit at the same time.
Their requests for your webpages are sitting in the request queue. Behind those of your vigilante neighbours.
But they have just so little time for indexing per website, that at the time your time slice is over, only part or worse none of your web pages could be parsed.
Believe me, BigG and BigY move on quickly. They don’t want to be haedline news at CNN or Al Jazeera for terrorising and breaking down an already overloaded shared webserver. Let alone claims from a few hundred hosting account subscribers and a hosting company.
You will not be banned. But you risk that your websites will end up on a higher SERP.
If you had at least one dedicated IP, you would have had your own request queue.

Normally BigG and BigY only ban on exact IP numbers.
But if spamming, phishing, illegal porn, and WHY are rampant in your “neighborhood” on each visit of BigG and BigY, they will ban the IP range with the same C-class, as in aaa.bbb.ccc.BAN.
So even multiple dedicated C-class IPs will not do you any good.
You can look up which IP ranges are in possession of your hosting company.
Some hosting companies offer dedicated IP packs with different Class-A, Class-B, and Class-C in one pack. That’s the only way to go.

Let’s say that you still do not see the point of dedicated IPs for SEO purposes. Fair enough, I’ll still buy you a beer.
But do yourself a big favour and get at least one dedicated IP on a shared hosting account for the nother reasons that I mentioned.
Because $12 – $24 a year for one dedicated IP saves you a lot of trouble.

Robertino

From first hand experience, I can tell you that I have scene literally hundreds of domains hosted over the same IP address, they are indexed and consistently return top 1-5 results for their respective product.

Does anyone know what the consensus is amongst the SEO elite?

Regarding using Whois info, that can be it’s own slippery slope. There are many companies that register domains on behalf of others, or design/webmaster/consultants that manage on behalf or lease out domains. Each of these domains have different owners but maybe the same Whois information. And what about private registrations? They all look the same for each registrar.

With the increase of social networking sites, it has become very easy to build your netwrok of links outside of your own servers.

The cost of hosting on different providers really isn’t an issue, if your monetizing your sites. It really shouldn’t be that difficult to recoup $10 for hosting on another provider or paying $1 – $3 extra for another unique IP.

Kevin