I'm not entirely sure I agree with that. You don't get spyware from IE being open, you get spyware from going to webpages with IE. I've got IE on both my main computers (obviously, since they're Windows) and I don't get any spyware. On the other hand, if someone found a hole in Firefox and used that to install spyware on my computer, I would still have spyware on my computer, despite Firefox's lack of integration with the OS.
There are issues with IE's amount of integration, like the fact that other apps can embed it and could then theoretically open up evil webpages, and that you can't change that plugin to Firefox (although this is, at least partially, due to the fact that nobody's implemented the API for Firefox. A lot of people suspect it would be quite doable to swap the plugin if someone would just write the interface needed.) But on the other hand I don't think I've ever seen an otherwise-benign app get someone infected by embedding IE. And having an HTML renderer available for embedding is a damn useful feature to have.
The only real problem with IE, IMHO, is that it's basically a monoculture and that it's recurringly buggy in exploitable manners. I've never really had an issue with how embedded it was, and I don't think (besides the monopoly leverage factor) that contributes at all to the spyware problem.
Re: If only IE was an application
There are issues with IE's amount of integration, like the fact that other apps can embed it and could then theoretically open up evil webpages, and that you can't change that plugin to Firefox (although this is, at least partially, due to the fact that nobody's implemented the API for Firefox. A lot of people suspect it would be quite doable to swap the plugin if someone would just write the interface needed.) But on the other hand I don't think I've ever seen an otherwise-benign app get someone infected by embedding IE. And having an HTML renderer available for embedding is a damn useful feature to have.
The only real problem with IE, IMHO, is that it's basically a monoculture and that it's recurringly buggy in exploitable manners. I've never really had an issue with how embedded it was, and I don't think (besides the monopoly leverage factor) that contributes at all to the spyware problem.