It has always seemed strange to me that Spock had so much
red matter on his ship. When Nero destroys Vulcan, he uses just a tiny drop that looks like about .01% of the total amount.
Originally, I thought that was because Spock needed enough to collapse a star, while Nero was just using it to collapse planets. But when we see the flashback from Spock's mind meld, it shows that he only used a tiny drop too.
It doesn't seem wise to carry around that much of such an incredibly dangerous material.