Aloha All,
I have been a happy and successful WWOOF host for over 4 years now (well over 100 WWOOF interns), and 90 % of all people we've hosted have been at least good, many wonderful. I have a detailed 2-page “Parameter Statement” which I send out to all who contact me to be hosted. It serves well to give them more information, more security about what to expect, and helps us winnow out from among the many applicants we receive to those that we have space and good expectations for. Visa info is crucial as we have many people from all over the world!
There are a few exceptions, though, of people who look great on paper, who get here, but who are disappointing or disappointed, and who have terminated their stay after a few days or who had to be terminated by us (People who break our hard rules of zero tobacco and zero drugs, which is prerequisite, or who constantly bicker/fight with other WWOOFers). I am also addressing WWOOFers who can't or are unwilling to do their part of farm work; farm labor can be real labor, as we all know. These very few may think we are solely a vehicle to have a beach vacation (despite all info provided), and then things don't work out for them and us: they become grumpy, unwilling, and are not the asset we need. That is the case in about 5%. Those few cases are bad for us because we plan ahead and such interns have then blocked spaces for others. Overall, again, I am very happy with and grateful for this program and I believe our success is based on good "front-loading": give them a lot of info so that there are few disappointments - for them and us.