Why would you mention "opting-in" without saying what they "opted in" for. The crucial thing here, was that there was no warning that opting in for sending data to Microsoft might lead to that data being used on their search engine. Again, this claim is more interesting in what it shows about Microsoft than Google.
The grandparent meant "opting in" to click tracking on the Bing toolbar. This applies just as much to Google as it does to Microsoft - it's ridiculous to claim otherwise. Google tracks your clicks and your browsing habits, and has never tried to claim otherwise. What do you think that onclick function on every single search result on Google searches is doing?
So the fact that Google doesn't know the details of the inside of Microsoft's system is their fault now?
You can use that to claim anything. Yahoo: "Hey, we made a search on Google.com and its top result was the same as ours! They must be copying our results! Why is every other search result different? Hey, it's not our fault we don't know the details of the inside of Google's system!"
What's worse is that there is a very clear and simple explanation for this. Microsoft knows that what it is doing is wrong. The copying is even more blatant than that (e.g. they copy clicks mostly from Google, partly from Wikipedia and other key sources and not at all from random pages round the web). Instead of making a fairer algorithm themselves they have spent effort on cloaking their copying. They only randomly introduce results and only after a random delay from the point where the results are clicked on. This is not designed to improve results by weighing up different factors (remember there aren't any other factors in these particular results).
Ah, here's the real meaty part. Let me call out one particular line.
they copy clicks mostly from Google, partly from Wikipedia and other key sources and not at all from random pages round the web
Citation needed much? I would love to see any—any—information about where the track click data (other than clearly Google).
It astonishes me that you realize how Microsoft was able to index these sites, and you still think they're at fault. They are tracking their users' click data—something the users implicitly opted into by installing the toolbar, just as you implicitly opt into Google parsing your emails by using Gmail, or Google tracking your clicks by using Google search, etc. The reason they were so high up is that the clicks were the only factor in their ranking—you said it yourself!
So now the question: what did Microsoft do wrong? They're simply taking the browsing habits of their users and using it to improve their searches. In this case, the only data available was the honeypot Google set up, so it ended up at the top. That's it, plain and simple.
