I wonder how many people throwing opinions around this were "of age" in the early-to-mid 90s and thus remember what an unstoppable behemoth Microsoft was.
This was a time when they had 95%+ of the desktop OS share and you basically couldn't run a home computer with Windows. This was the early days of Linux (IIRC in ~1994 I downloaded SLS running Linux 0.99.x onto ~30 floppy drives over a 2400 baud modem!). Macs were an expensive niche product. Personal computing just wasn't possible without Microsoft.
Microsoft very much used this position to kill Netscape as they saw the Internet as an existential threat (fearing Netscape would be the new OS). They tried to subvert Java (the threat of "write once run anywhere" being a threat to the Windows lock-in) and partially succeeded. It was at this time that the DoJ stepped in.
I can't overemphasize the perception the tech community had of Microsoft then. Windows was rapidly evolving. Windows 95 was, I believe, a major turning point for the company (and where it achieved at least technical superiority over MacOS having preemptive multitasking and dynamic memory management). Microsoft really had an aura of invincibility.
We are not in this situation today. Apple seems unable to do no wrong (in the marketplace; there are what are still fringe elements criticizing them for any number of things) but don't have the market position Microsoft did.
In fact, Microsoft doesn't have the position Microsoft did in the 90s. At this point I believe we have viable alternatives to personal computing between mobile devices, Macs (you can get a Mac Mini for $600), netbooks and--dare I say it--even Chromebooks (you'll note that I left Linux off that list as I believe it will never be a viable mainstream desktop OS and of course I know it powers Android/ChromeOS).
I certainly don't see an issue (yet) with Apple blocking alternative browsers. Don't like it? Buy an Android. Or a Windows Phone 7. Or a Blackberry (OK, I couldn't keep a straight face with that last one).
Windows and Office are the geese that lay the golden eggs in Microsoft. Everything is beholden to them. As an organization, Microsoft seems terrified they'll die and as we've seen time and time again it's that fear and that switch from innovation to defending your turf that ultimately leads to the death of companies.
I believe the whole Metro API browser thing is just more evidence of Microsoft's stagnation. Let them I say. It'll probably, at least in some small way, hasten either their demise or them attempting to turn the boat around before they go off the cliff.
EDIT: yes Netscape was complicit in its own destruction. I used Netscape up until version 3. By Netscape 4 on a 486DX4/100 at least, IE4 was significantly better and faster and I never switched back (not until Firefox 1.5/2 years later).
Netscape eroded at both ends (IMHO). At one end obviously was Microsoft giving away the equivalent to their consumer product for free (as well as bundling it with the OS, making it harder to use non-IE browsers and so on). At the other end was actually Apache. The Apache Webserver I believe it incredibly difficult to build their server software platform (anyone else remember Netscape's Web servers?).
It wasn't until the rise of search engine advertising some years later that Microsoft's hold could be broken, it being the only thing that makes Firefox and Chrome possible.
As an aside to all those who are anti-ads: how exactly would non-OS browsers exist without advertising?