What could a web2.0 virul look like? Here is my guess:
- it will be written in Javascript
- it will live inside Google Documents
- when you open the infected document, the js will look up your Google contacts, create an infected document and invite all your contacts to collaborate on it.
- when one of the persons invited opens the infected document, the virus will replicate, and so on.
How could a virus like this be damaging?
- it could delete your mails, your documents, contacts, etc.
- it could do some URL rewriting to add a specific associate id to links to amazon and other on-line stores.
- it could launch a distributed DoS attack agains a site…
Replace Google with Microsoft Live above to get a more destructive effect.
I’m pretty sure this will happen sooner or later. And then we will start looking for the Open Web2.0 platform that has fewer virusses, etc… 
We know from research that 49 per cent of attacks to the industrial network come via the corporate WAN and business network. It is also widely accepted that 80 per cent of firewalls are incorrectly figured which makes securing the production network a real area of concern. What these figures illustrate is that the probability of Web 2.0 malware being transferred from one environment to the other is very high -and to disastrous effect!
Viruses are becoming more complex and companies need to address the increased threat by investing in decentralised security devices. Budget and size will determine whether a company selects a plug-and-protect solution, or a decentralised firewall, but in either case the core message is – get the security closer to the machine!