I think I've said "catastrophes" before rather than "disasters" and I think that's a better word, but I stand by it.
It doesn't matter that Rabbit doesn't intend harm. Neither does Tatja, at least to those who aren't trying to harm her. But well, look at what she does, at first she almost gets a few dozen people killed, reckless teenager but hardly extraordinary, next time we see her she's about to tear apart a kingdom to fraudulently seize power, and as collateral she's (without telling them) ensured everybody she knew previously will die if she fails. By the end Tatja has started a war in order to seize control of a means to signal off world. Only two other people on her world even realises what "signalling off world" would even mean, but she's potentially going to kill huge numbers of people to achieve it anyway. She's a catastrophe even though that wasn't her intent. She does apologise, for whatever it's worth, right at the very end, to people who were close to her and from whom she belatedly realises she is now so distant.
Rabbit is indeed just playing. When the library nearly falls over and kills a lot of university staff and students, that's just a small taste of what happens when playful Rabbit forgets for a moment that this isn't really just a game. Consider just how powerful Rabbit is remembering that's a distraction. The whole fight, which causes massive disruption to the city and easily could have led to enormous loss of life, isn't what Rabbit was really doing, it was just to distract Bob's team so that they don't focus on the labs for a few hours. And remember that Rabbit's goal here is clearly to secure the weapon for itself, not to deny it to the antagonist.
This is a compelling argument, but I think it's overly pessimistic. Back on the human side, the ending sees Robert adapting to his situation; he loses his left arm (his "sinister"), and it looks like he's lost his wife for good, but he's managed to find some amount of synergy with the new world and technology he's surrounded by. Combined with Rabbit's temporary "defeat" (an experience that, if he's truly a super-intelligence capable of true learning and growth, should lead him to different means and even ends in the future, if nothing else), the implicit conclusion seems to be a future with an imperfect but livable melding of humanity and technology. Not too different from what's come before. Putting all of human history onto a single drive likewise might seem like a diminishing of its significance, but the fact is that it's still there to dive into, should one desire. That's arguably a step up from the past.