Guy:
If everyone who doesn't read/score every story does that, then it all averages out and you are being fair to all.
If EVERYONE does it then, yes, you are being fair int he sense that no one has an advantage, but it also tends to randomize the "winner" rather having it based on the quality of the story, since some stories will inevitably get more reads, and therefore more votes, than other stories. Since most voters tend to award 5 or more votes to ANY story they read, the winners of the "reads" lottery will be the leading vote-getters. Randomization of which stories voters read in no way guarantees that all will be read equally. And since many readers wil NOT read randomly, but will read in order loaded, the "views" selection will NOT be totally randomized, but will be weighted towards the first-loaded stories.
Guy:
Another perfectly valid approach is to read and score the stories that most appeal to you. This approach gives those who craft good titles a slight advantage, but titles are important.
Although a title is important, this approach makes it ALL-important, making the challenge in essence a "best title" challenge.
I realize that as more and more people decide they can't finish reading all stories as the number of entries grows, they will need to develop strategies other than the drop-out approach if the reading/voting isn't to be left entirely to a few people with enough time on their hands. To the degree that the "best" stories didn't win before (everyone will have his/her own opinion), this will only increase as fewer and few people are able to read and vote on all. Is that a bad thing? Not really - the challenges were never intended to be about winning and losing in the first place.
ADDENDUM:
Giving it more thought - if you follow Guy's approach - reading randomly and scoring what you read - will be both "fair" and relatively merit-based IF the voter then gives an "average" score to every story he/she hasn't read. This should be not be a minimum score, or arbitrarily a "5," but rather the true average of the scores he/she has given every other story. That wold be my recommendation for everyone who can't read all the stories but wants to participate. Note: the numbr of stories you've read, plus the total number of votes you've cast are shown right under the contest picture, so you merely divide one by the other to get your "average."