mrV said:
What about freedom of speech? Should it be always good things to say, nothing bad?
If you say how things really are and not telling any lies, then they don't have any reason to sue you. And if they sue, they don't win, because you was talking only how things are. (I don't know how judicial system works in usa, where you can sue everyone about everything

)
Although it would probably be better if you tell about your experiences on your own homesite.
From the limited bit of journalism I've done it seems that Freedom of Speech is a defence in some countries (USA, for one) but in UK it's more complicated than that. OTOH, you're less likely to get sued in UK.
However, in most democracies that rule seems to be that if it's factually
true you can say what the heck you like. The problem comes when you have to prove what you said was factually true (a potential nightmarish hassle) and when stating opinion as if it's fact.
For instance, if I say "I went to Fishes-R-Us [a company name I just made up] and hated the service there!" that would be OK because it's obviously just my opinion.
If I say "I went to Fishes-R-Us and they were abusing the fish", I have effectively accused them, in public, of something likely to damage their business. They'd have a perfect right to sue, and I'd have to provide evidence the my accusation was true (i.e. that I hadn't libelled them). However, in reality, unless you're a prominent person, it is unlikely most companies would actually bother. The exception is companies with aggressive legal departments and massive bank accounts, and prominent people on the Internet who are unaware of their prominence - then be afraid, be very afraid!
The journalistic get-out clause is when you say stuff like: "One woman I interviewed, who declined to give her name, claimed to have witnessed an incident in which staff from Fishes-R-Us were treating fish in an abusive manner..."
That way
(a) It's not me saying it, it's "one woman I interviewed"
(B) I only said she "claimed", I didn't state it as fact
© I stated the facts of the claim (that she witnessed an incident) not an opinion. I could justifiably claim that ofcourse
I didn't think it was true!
Just to cover myself further, I'd then try to get a statement from Fishes-R-Us's Press Spokesman:
"...but a spokesman from the company said that investigations into the incident had not been able to find a shred of evidence to substantiate it."
The more serious your accusation, and the more at fault the company, generally the more likely you are to get away with it. Plus in UK you have to prove "material damage" ie. the claimant has to prove that they have actually lost physical money as a result of the incident. I'd suggest Trading Standards and the RSPCA would be better people to go to as a first resort, if you live in UK. They have the legal powers and can actually do something.
[Any lawyers reading feel free to correct me if I'm mistaken at any point - you might be sparing me some trouble]
So, say what you like but make sure it's what's actually happened, that you state opinion as opinion and if necessary you give the company the chance to give a contrary opinion. Alternatively, Publish and be Damned!