Having the opt-in vs. opt-out discussion is worth while. But calling this feature "spyware" is total FUD and only serves to alienate the hard-line Free software proponents from the rest of Free software society. To be frank, I stopped listening to anything Stallman had to say a long time ago. because to RMS and people in his camp, this is a religious issue.
To those of us living in 2012, though, there's a real discussion to be had. I thoroughly enjoy, though rarely use, the Amazon Unity lens. I would find a Google lens significantly more useful, in fact. Because hitting the menu key, and typing in a Google query would save me from opening a browser, clicking CTRL+K, and doing the same basic thing. The utility of offering me music, books, and merchandise when I type something into my search bar is extremely useful.
Now, as to the "spyware" claim...that's total BS. The term you've typed in your Unity bar is sent to Canonical and then to Amazon. I would like to know what the difference is between that, and simply searching Amazon? Because either way, I have an IP address to tie your search back to. But, since we live in a world where it takes some work to discern if there are multiple devices behind a single public IP, or who is actually behind a public IP, the utility of the "spy" data is of serious question here. Great, so Canonical knows you searched for "term..." several times a day. Or, heaven forbid, they know you searched for "Kanye West" while looking for an admittedly poor musical choice. This is data that Amazon already collects. As well as Google, and whomever else may be selling you musical tracks or providing search functionality.
The fact that the feature is on by default is probably due to the fact that Ubuntu tries to accommodate the "average" computer user. This user is not like the "average" LWN subscriber. They find a serious utility in making things easier to access, and they put serious stock in the idea that the entire Internet isn't so far away from them. Yes, to you and I, we know that a browser window is almost certainly open somewhere, and we can go directly to the source of our content and search. But my mom has literally no idea what the difference between a browser window and her desktop area is. And Ubuntu has made serious strides in getting people like my mom onto a far superior platform than Windows.
If you don't like it, disable the lens. If you do like it, keep it enabled. If you believe strongly that after a user's first login they should be prompted to enable things like the Amazon lens, then suggest that to the Ubuntu developers.