Yes, a great number of these spammers are not real people, but automatically generated spam-bots.
The ususal thing is to send out one piece of malware in the expectation that it will infect thousands of inadequately protected computers....and then these infected machines can be grouped into a bot-net and used to transmit spam to all and sundry.
So as well as the forums/sites trying to protect themselves from these attacks, we can all help to keep the internet clean by making sure that our own PCs are clean, malware free and thus not being part of a bot-net.
These can be dangerous in that they can keep replicating themselves and thus sent out an ever increasing volume of junk.....and a lot of that junk can be dangerous if you happen to click on any links contained within them...sure fire way of arriving at a very bad site.
On the question of the specific site you refer to, yes that site may have been compromised and may require a good clean.
