I am not sure there is much (if anything) random in the assignment of votes. Allocation of votes is based on fan pools and player performance. This means that players that have performed well and belong to teams with large fan pools // have been seen by large crowds will be selected.
Also, I am not sure that the participants in the 3-point contest are necessarily picked by the voted allstars, but it has never occurred to me to check one way or the other.
"I don't know half of you half as well as I should like; and I like less than half of you half as well as you deserve."