They address why this even happens on Stack Exchange Podcast #2Stack Exchange Podcast #2 as a way to remind people to upvote useful and helpful questions:
Jeff Atwood:
Now, one thing we have done to help with this is if you come through a web search engine and you arrive on say Stack Over, or Server Fault or any Stack Exchange site, and you actually hold a cookie for that account, meaning you have an account on the site and you are able to vote, we will gently remind you, "Hey! You arrived here through a Google web search. If you found this question useful, please vote it up and the answer."
Podcast time point: 51:24
Because, if you found the question through an external search and it's helped you, or it's well written, bump up the question with an upvote.
It helps with their algorithms on what to show regular users. Like the one that is used to float the good questions that deserve more natural attention to the top over the dregs.
Joel Spolsky:
Question score will make something more likely to appear on the homepage. So we need to teach people to vote up questions that are well asked.
Podcast time point: 48:15
