I took it to mean that it was blown up because of Leia's connection and to get at her, and not so much because it was important.
Ah, but as Tarkin does say:
Tarkin said:
Dantooine is too remote to make an effective demonstration.
Tarkin may have blown up Alderaan anyway even if the base was ideally situated (he is that kind of jerk), but it seems that Dantooine was so obscure a world that its destruction wouldn't have the fear-inducing impact the Death Star was supposed to be about.
But it does strike me as odd that while she's supposed to be in hiding from her father, that she was wearing the Princess role. That likely made it easier for Vader to track her down.
Leia wasn't hiding. The ship she was on was, officially, a courier on a diplomatic mission. The Tantive IV is going about very public business, and the star destroyer's sudden assault is quite arguably illegal. She was using her status as Princess as a shield and cover, basically, and it's only at the start of the film that she's summarily accused of being a rebel.