I have downloaded, and frequently run, the new Microsoft Anti-Spyware and found it to be very good. My concern is about how long this will remain a free product.
Microsoft has, in the past, given software away to gain marketshare in areas in which it is not dominant. Internet Explorer would be the obvious example, although this was based, IIRC, on the free Mosaic browser. Hotmail, on the other hand, was acquired to compete with AOL and cost them a lot of money but continued to be free - I assume it still is.
My guess is that they may just see free anti-spyware as a simple, and relatively cheap (compared to actually fixing Windows), solution to some of their more pressing security problems. The continuing virus and malware problem is all bad publicity for the company, and they've been sensitive to that in the past. Gaining marketshare with a freebie and then leveraging the monopoly is a tried and tested Microsoft technique, but while paying for a product that fixes security holes is one thing - we've been doing it for years with Anti Virus software - it's a rather bitter pill to swallow when it's fixing holes in another product released by the same company. They might also be open to claims of unfair advantage - Microsoft have access to the source code for these problems, while their competitors don't, so they'll have to be a bit careful. However, it wouldn't be the first time, so I guess that was a very long-winded way of saying "I don't know"
