The risk of getting a virus-laced Valentine's Day e-card is on the rise. The FBI has issued a warning about cards carrying the Storm Worm virus.

It may be due to the fact that Valentine's Day is a giant holiday for greeting cards, or it may be because people as a whole are getting very lazy and cheap, but the use of e-cards is on the rise. This provides a perfect opportunity to spread malware.
The Storm Worm is one of the big viruses that is eager to exploit your love, lust, and laziness to attack computers. It comes by way of an e-card that requires the recipient to download the card, which happens to be malware.
The Storm Worm is a botnet that turns your computer into a work horse for the controllers of said virus, allowing your machine's power and Internet connection to be utilized for spam, identity theft, denial of service attacks and more.
The general rule is do not open e-mail when you are not familiar with the sender. Then again, if you haven't been following this rule since the beginning of the Internet, then Valentine's Day greeting cards are the least of your concerns, and you should really get your PC checked out.
With the coming of the holiday, you may start getting some ecard spam. Here is a brief refresh on ecard safety.
A legitimate ecard email will include the name of the sender in the email subject and the email body (with the email address). Some ecard site allows customization of the email subject by the sender. But the sender name and email address should always be in the email body. If you don't recognize the name or the email address, then delete it.
In addition, you should always have anti-virus/anti-spyware application installed on your computer.
You can get the free security applications here.
AVG Anti-Virus Free Edition
Spyware Doctor and Norton Security Scan from Google Pack (or search on "Google Pack")
Also you can also install free McAfee SiteAdvisor that will warn you if you are visiting suspicious/bad websites.
As usual this advice is wrong. You are much more likely to get a virus laden email from someone you KNOW not someone you don't. Most viruses send from the users address book. I can't believe after all these years writers still get this most basic fact wrong.