The GMAC is a monopoly, so I suppose it can do what it wants, but a little bit more transparency would go a long way. As far as I can tell, there has been no official announcement of this new policy, almost as if it intentionally wanted to bury the news to avoid controversy. At least the GMAC summit is coming up soon, and I'm sure that this topic will be broached by GMAT Club representatives.
I also take issue with the wording of the post, which I presume was written on the last day of November or sometime shortly before then. "Lifetime limit updated November 2016" makes it seem as if there were already a lifetime limit in place, when this was clearly not the case until the day this news was released. You can't update something that doesn't yet exist, so it would be more accurate to write "lifetime limit implemented November 2016" or something similar.
I do agree with bb that this policy will help mitigate the outsized advantage that richer students possess, where they can simply just keep taking the GMAT (and cancelling their scores) until they receive their desired scores. The GMAC would be wise to play this angle, as makes sense from the egalitarian perspective of "leveling the playing field" for students who can't afford to shell out $2,500 to take the GMAT 10 times.
If you think about it, there was a 5-test limit every 12 months, but you could conceivably take 10 GMAT exams in a 15-month span, once the required duration between tests was lowered from 31 days to 16. That strategy obviously won't work anymore, since you are capped at a total of 8, including cancelled scores (but probably not cancelled test dates or postponements).
I've never known the GMAC to turn down an opportunity to make money, though, so there is likely an ulterior motive at play. Maybe the test writers are also trying to prevent tutors like us from getting too familiar with the test content and the scoring algorithm, even when we are following the rules and paying for the test like everyone else.