If you feel a host is abusing the spirit of WWOOF then you can, and should, write and complain to WWOOF Portugal.
However, one of the problems that hosts encounter is WWOOFers who have unreasonable expectations and who have a strong sense of entitlement because they are offering their labour. This offering of labour is an essential difference between WWOOFing and couchsurfing.
I have on two different occasions received a WWOOFer (both were first timers) who thought that hosts should adapt to the WWOOFer's normal meal times, their diet, their room choice, their choice of day-off, their Internet needs, their task preferences, their preferred sauce flavourings, their clothes washing routines etc. These WWOOFers then rallied opinion with the other WWOOFers and asserted that the other WWOOFers wanted change too and I should concede to the democratic opinion.
First of all, my farm is MY home. It is NOT a democracy.
Although I do try to accomadate WWOOFers needs, there is a difference between needs and preferences, and a WWOOFer who expects me to run my farm in way that better suits his/her wishes is very difficult to host, especially one who tries to pressure me by claiming to know other WWOOFers needs and opinions.
Running a farm is much more demanding on hosts than most volunteers realise. Hosts have to plan, delegate, supervise and adjust work tasks, plan and cook meals, socialise, maintain moral, instruct, enthuse and praise volunteers, solve problems, shop, prioritise work, assess volunteers abilities and aptitudes, and more.
WWOOFers have considerably less to organise and monitor. I agree that both hosts and volunteers should adapt to each other, but I assert very strongly that this is NOT a symmetrical obligation.
Disgruntled WWOOFers who don't understand this asymmetry very likely would write poor reviews. Probably in a few short lines. For readers to understand why that review is unreasonable a host would need to write at length to justify the way their farm works in order to restore confidence from potential WWOOFers. This is not somethings I would be happy about having to do after a dissatisfied and demanding WWOOFer has finally left.
As a dissatisfied WWOOFer you should first talk to your host. If that doesn't help then you can simply leave early, tell the host why you are leaving early, and tell WWOOF Portugal why you are dissatisfied.
If you still feel you want to name and shame, then there is nothing to stop you setting up a blogg for WWOOF host reviews.
Many WWOOFers conflate 'reference' with 'review'. References are disclosed at the referenced host's discretion, who requests them from WWOOFers of their choosing. Review's are outside of the reviewed host's control. This is an essential difference. References illuminate the positive qualities of farms. Reviews can be very negative and very unfair, written by people with unreasonable expectations or personal rancor towards a host.
WWOOF Portugal has chosen a reference system, not a review system.
Quinta do Barbeito