I do not use these services too often, but I really enjoy them when I try it. I liked Yahoo! Answers when started, but I stopped using it as the answers started to low their quality. I also tried Google Answers some years ago and the quality and process were great but all of us know what happened it (the rumor is that they will open it again in english as they keep using it in Russia). Paying for an answer is not a problem to me when I am looking for something and I do not have time or its more sophisticated than usual, for that Mahalo has been very useful during the last months.
Well... other services for specific verticals like Sermo or Symposier for physicians or some others to ask questions from patients to physicians are also great services, but the experience its very similar in all of them (it is not bad) and we do not know if it is the best or if there are better alternatives for the asking and answering process...
I tried Aardvark for the first time this week and the usability is great! you interact through your IM client, not only to ask but also to answer. I like also that you set up your expertise areas, so you start your collaboration process without going to the site. I really do like that.
My comment it is not about just these social search services, but about how to keep challenging the process definition, user interface, usability, etc.
Aardvark challenged the standard process and I think will become a very good alternative. What do you challenge you on your site, brand, product, service, etc? We always have to challenge our utility, usability and likeness!!!!
A best practice should be a base line to us and not a mandatory process or UI to replicate
The year 2010 will start in 48 hours! let's challenge our all and push to be always better!!!!
Enjoy the 2010!