The Conficker Worm that people were so hyped up about for April Fool's was nothing more than a piece of malware that preyed on a system's vulnerabilities. The issue withstanding is that the official patch for that vulnerability was released late last year. We're currently four months into 2009 and people are still be affected which means that they haven't done any sort of updates.
I stated in on another forum, but people have ignored security in replacement of speed. People are so worried about having fast internet that: they don't take the time to keep their anti-virus updated, they don't have running firewalls, they don't do their Operating System Updates, and they don't actively scan their systems at least once a month. Perhaps the biggest issue is that they lack the education or just don't care. They get a new system that has McAfee/Symantec/Norton and the Windows Security Suite - then: think that they're good to go OR they notice that those programs bog their system down... so they disable and don't get anything else.
I don't know if this is allowed or not (If it's not, please feel free to remove it) but for those out there without protection, here's a few programs you should look at getting in order to keep your system clean without bogging down the speed (like McAfee/Symantec/Norton). Not to mention, each of these is completely free for home use. ((There are upgraded versions that you can pay for, but they just give you extra features))
Anti-Virus:* AVG or AVIST
Anti-SpyWare/MalWare:* Ad-Aware
* SpyBot Search and Destroy
Firewall:* ZoneAlarm
For those who do a lot of internet browsing, I would also recommend a monthly run of TrendMicro's Free HouseCall scan. You get these programs, keep them updated, have the firewall and anti-virus active at all times, run the Spyware programs once a week, and do monthly HouseCall scans - you will be good to go.
But hey, for those who don't want to keep their systems protected... you're just keeping people like me in business.