Email spamming, if considered blackhat, is illegal, at least in some countries.
Very little is illegal on the internet in the UK
A fair bit more in the US.
But the term that needs defining here is "Black Hat"
And people need to understand that breaking the terms and conditions of most sites is not "illegal" it is, at worst - "actionable through civil law" if the site owner can prove it has incurred cost to them,
If you are scamming adsense with false clicks - that's theft.
If you are sppfing CPA actions for cash through affiliate deals - that's theft
Criminal - simple as that. Internet or real world. It's most likely a "time inside" crime. Your safety at the moment is in "anonyminty in the numbers" you are one of tens of thousands doing it - you are likely small compared to those that are doing it on an industrial scale.
However, as the numbers dwindle, you will stand out more and more.
ON THE OTHER SIDE
Making 300 accounts in Yahoo mail, or setting up 150 Wordpress.com blogs or Youtube accounts is against their TaC. They can ban you, they could take civil action if they wanted, but it is not (in most of the world) illegal. Your just being a pain in the ass to them.
If you then use those Youtube accounts to scam them out of "cash for views" - then you've crossed the line. If you use your email accounts to try and get pensioners to hand over their insurance details to you - you've crossed the line. If you promote racial or illegal activities on your wordpress.com accounts...again you've crossed the line.
The law on theft, race hate, forgery...well that's the same whether it's on the internet or not. They catch you - and your found guilty - you spend some time in the hot house. The fact you did it on the internet is irrelavent these days.
Annoying Wordpress or making the Yahoo servers work a little harder for some other purpose (perhaps just putting a ton of content all over the web to promote your site) is, in most countries NOT illegal.
However, in the US...it is - at least technically.
The chances of anyone looking to extradite you for posting 1000 articles on WEB2 sites, or submitting your RSS feed to more aggregators than would seem appropriate for the conent...well, let's face it, that's not going to happen any time soon..US based or not.