physics - 11:15 pm on Nov 20, 2008 (gmt 0)
The issue here is that Microsoft may be the last company you should trust to do the best job of writing antivirus software for their own products, strange as that may sound.
It's like a police officer asking a parent to tell all the worst things about their own kids to the officer. Probably not going to happen and even if it does the officer wouldn't trust it.
Now, ask some other kids at school who don't like the kid and you might get some more interesting info.
The other kids at school (McAffe, Symantec, et all) might not have as much internal knowledge about Microsoft's products - but neither do the virus writers.
To put it another way, if Microsoft is their own antivirus company then who watches the watchers?
Microsoft's job is to harden their OS and apps to reduce the POSSIBILITY of viruses, malware, etc. That's where they should put their resources.
All that being said, something is better than nothing - but you can get SOMETHING for free from other companies anyway.