If the reason for a boycott is based on the perception that they would not enjoy the entertainment offered, then it is not a boycott. Whether it be because they are so in love with TOS they couldn't handle the reboot, of if they think the Spock/Uhura romance ruins the film.
The Montgomery Bus Boycott was not based on the lack of bus-quality, or the readilly available better options. Any so-called "Star Trek" boycott is.
Some people chose not to see "Star Trek" and some people chose not to see "Meet Dave" with Eddie Murphy. If the reason is because they don't think the movie is worth seeing (which, expressed at great length, is what most TOS 'boycotters' seem to say), then calling it a boycott renders the term completely menaningless.
If you would otherwise purchase the PT, but aren't out of protest for Lucas's actions, that might be called a boycott. If you don't want to purchase the PT and don't, that's not a boycott.
One might organize a boycott of Twilight because it promotes violence against women.
One cannot organize a boycott of Twilight because it's not worth seeing. Although one might try to persuade people to your opinion, if they joined you they still would not be boycotters.
People not seeing movies they don't want to see is how the entertainment industry works. A boycott as a political tool is by definition a purposeful change from the normal working of that industry.