The key question here is "Are you using their name to get visitors / trade / profit?"

If you are, and their name is trademarked - or otherwise protected - then they have a variety of actions they can take against you, including shutting down your site.

If their name is not protected (eg they are called Table!), and your site has no content related to their products, then you have little to fear.

Anything in between, get specific advice.

But if THEY were using YOUR brand to make a profit (and thus depriving you of that business), how would you feel about THEIR web site? ;)

See an attorney. If you can't afford one, you have no business doing this.

My understanding is that there are some situations - such are criticism, satire, etc. - where this won't run afoul of trademark law - but EXPECT a fat legal bill defending yourself anyway if your target is high-profile or just stubborn.

Keep in mind that in the American legal system, anybody can sue you for anything. There's no examination of lawsuits for validity at the time that they are filed, and it's going to cost you - time and money - to respond.

So, it's prudent to avoid doing things that might prompt people to sue you.

In addition to potential legal action, not only could a trademark holder force you to shut-down, but they could acquire your domain name, without any legal action whatsoever:

See the ICANN UDRP:

[icann.org...]

And the supplemental rules of the various dispute-resolution service providers:

[icann.org...]

Basically, you've agreed to these terms through your registration of a domain name. Your agreement with your registrar will reference the UDRP.

I make no money from the website. The only thing I have is a message board for that companies employees to communicate. I used to work for the company and started the message board while employeed. When I left I kept the board running. I have no images or copyright words on the site. The companies name is also the first 5 letters of my 9 letter website name. I have done some research and several thousand other website are using the same 5 letters and many are porn sites. Of the other websites I have contacted none of them have ever been contacted by the company who is threatening me.

If you are allowing 'anti-company' stuff, then they have a cast iron case against you, as you could damage their reputation.

Face it, they've called in the lawyers. You either do the same, or you act before they take you court.

How deep are your pockets?

To paraphrase one of Webwork's constant refrain against posting specific personal details about legal situations:

"Best to shut up now, before this post becomes Exhibit B."