Well it depends....

Firstly not everyone uses their internet at home - if you use free wifi, such as Panera bread or some other service which doesn't require a logon or credit card, there is zero chance they can find you.

Secondly, if you connected from home, depending on what you wrote online (I'm speaking more generically here), they would need to prove who did the actual posting. In a household with multiple people, it would be hard to prove who posted something, especially if it's a new screen name without a history.

So - if you wanted to post something in complete secrecy with absolutely no way to track you, you can do the following:

1) take your laptop to a free wifi location, or

2) use a cash-bought debit card at a Kinkos or other computer place

If you have a screen name with a history which could identify you, make a new one for these types of sensitive postings.