I was considering hushmail until I read their terms of agreement which clearly state that if they find your email is being used for illegal activities they'll report it.
If I have my email addy on my site and TER wouldnt that be enough for them to shut it down or are they just saying that for legal reasons?

What to do???

I've never had any problems using Yahoo.  It's easy to set up an anonymous account with them.

"Hacking" is much more complicated than you'd think...  Involves breaking the codes of the ISP.   I do a lot with on-line boards & P/Ws...  most account problems are "cracked".  Palin's account was "cracked" using her security questions...  figure out the answer or lucky guess.  There are dictionary programs which will try to break passwords.
Secure password with a combination of letters, numbers & symbols...  not a dictionary word.  

A Favorite lady lost her working account to a phishing scam...  never got it back despite repeated attempts.  

I think all ISPs include "illegal use" provision.  
skb

Let me answer this in two ways:

Security:
Google probably has the tightest security of anyone. If anyone is going to get "hacked" or "compromised" it's going to be on your end.

Legality:
Having an email address on TER is not an illegal activity. The contents of your correspondence may or may not refer to allegedly illegal activity, which is probably the last thing google is worried about. I'm not familiar with hushmail.
I'm not advising that you create an alias on google, but it can be done.

You could host your own, if you know any geeks that would help set it up for you. It's painless on a mac server.

What exactly is your biggest concern???

just google the phrase "password hacking services " and you'll see that for a few hundred dollars, there are foreign services that offer to hack any account for a fee.

because many many clients use yahoo...

Why is that?  Was considering switching to Hushmail.

You might want to try mutemail.com.  They are an offshore anomizer (I am not sure I spelled that right) e-mail outfit.  They are based in the UK and the servers are somewhere else.  They are about as secure as you can get.  

Or, get an e-mail account in a country where prostitution is legal.  There is little chance of any cooperation in that event.  And, any type of international cooperation on anything legal is expense for the government involved, even for a real crime.