Don't get me wrong, I agree that MS is coming across as stingy. I have interpreted their actions to mean that they wanted to cut back on the people who were given extra free storage but weren't spending money on MS services. It seems obvious that they are now targeting a different audience--the Office365 audience that typically buys a variety of MS services (think Work & Play Bundle customers). It's also pretty clear that they wanted to align themselves with the Apple model for free storage (5GB). I'm not saying it's good or bad business because I don't know how it will shake out. The issue we are talking about stems from a group of posters that I feel come across as overly-entitled. I've given my reasons for that and at this point am probably beating a dead horse.
Of course I think the best plan would have been for MS to directly link the 30GB with "the phone" but that's not how it was set up. It's tied to personal accounts, so you could have bought a Lumia 520 for pennies, get your 30GB, sell the phone a day later and keep the 30GB free cloud storage. Your desire, while a good one, is not enforceable. Nevertheless, they must be aware of the issue because eliminating cutbacks for customers who are using more than 5GB until 2017 dovetails with the useful lifespan of existing Lumia devices.
With respect to your "for life" example, the advertising needs to say "for life" or "for two years" or some specific duration; otherwise, a consumer should read the terms and conditions. Those terms clearly say in several places that the terms can be modified on notice. Should MS have been more upfront about it? Absolutely, but they probably intended to give the storage out indefinitely, then did an audit of the service and realized that they were losing a bunch of money in those two areas: >1TB and <30GB. If there's one thing I've noticed about MS and other tech corps, it is that nothing ever stays the same. Deals come and go, services come and go, and people should expect the unexpected for it will happen. And read the small print--it matters.