pg, the world of Windows software is grim, but mostly it's because majority of users are not tech-savvy. It's not that they are willing or not to click through buttons, they simply don't know what they're doing. I've seen this countless of times, and cleaned up many more computers from the results of such installations. IM might not be misleading anyone, but it's mostly because you cannot mislead a person who doesn't even listen to you.
All in all, whether or not IM will make Windows software space worse depends strongly on how they'll select the advertisers. It's a lot of trust to be put in a company, so no wonder people are sceptical.
I also think that GoDaddy is a very low standard to compare to, much, much lower than what we came to expect from YC startups.