Many people say that bouncing will only show that the e-mail address is active and so you will get more spam. This might be true in the general case, however, if you read Mailwasher's help file you will find that this point is addressed. MW says that the bouncing is done in a way which makes it appear as if the ISP has done the bouncing. Bouncing does create more traffic on the Internet.
The problem is Gazzerr that the "from" address is pretty much guaranteed not to be the spammer.
Imagine your email address was being used (spoofed) by a spammer to send thousands of emails... if all those people bounced back and the responses came to you you wouldn't be too happy.
Also consider getting a mail filter that can look up spam databases which are updated in real time. As soon as an IP address is known as a spam sender they get added to these lists, your machine then immediately rejects an email with a header containing that address. At work we filter out hundreds of emails a day using that technique alone.
There are various initiatives to cut it down. 'All' it needs is a way of validating that the sender of an email is actually who they say they are. The problem is getting everyone to do it at the same time, or even gradually.