Virtual Firewalls (and other network devices)?
There's a very interesting article over at Replicate Technologies (Which I found via the VMTN Blog)on using Virtual Machines to replace your network devices... (Firewalls, VPN Concentrators, Load Balancers, Email Filters, etc) and I think it makes a lot of sense... Why buy a new box to handle your email filtering when you can hop over to the Virtual Appliance Marketplace and download a system to do it for you... Why stick a firewall in front of a machine when you could drop a VM Firewall on it and use some fancy networking-fu to firewall the box... These eliminates the need for additional devices clogging up your data center... and for a small business let's you have maybe two servers instead of servers and additional devices...
Here's an example of it's use... I know of a company (15-20 employees) with a Windows 2000 Small Business Server... SBS is the worst design ever... Exchange on your DC, which means your DC is on the internet. Everyone knows that there are security risks associated with these... and the company didn't want to put out the money for a second full server... They also had spam issues (which they paid a hefty Trend Micro licensing fee to deal with)... Being a small business, they could have dropped the Trend Micro licensing and purchased another 512MB-1GB of RAM and implemented the Email Security Virtual Appliance. The ESVA could have been live on the internet, the DC would be behind another machine, and they wouldn't have had to buy a new server...
The future of Virtualization is a hot subject right now (See here and here)... and I'm glad to see it's not being easily dismissed.