DanUK wrote, "They may just not wish for any repercussions."

That is an example of cowardice.

I can think of another semi-rational reason for an anonymous account, that is when your identity distracts people from the point you are trying to make. Your identity could cause people to misinterpret what you're trying to say, where if you posted the comment anonymously, there would not be that filter getting in the way. This has happened to me a number of times on Ax. Since I'm the site owner, people sometimes (mis)interpret what I'm saying in a particular way.

However, avoiding misunderstandings is another form of cowardice. Misunderstandings are a part of life. We naturally interpret what people say largely based on what we know about that person. It's part of our survival instincts. It's part of how we evaluate the people we choose to trust.

I think people have a tendency to hide certain ugly parts of their personality. For example, on Facebook, people tend to use their real identities (because that is how people find you and you build up your friends list). When people post their strong opinions on Facebook, they can lose friends quickly. I've seen a lot of examples of this. I've personally defriended a few people and I've been defriended based on thoughts being posted on FB. The things you say on there are tied to your identity and you have to take the consequences of your own thoughts. It can get ugly sometimes, but I think the result is good. The lack of anonymity on FB adds a mechanism that isn't common on forums.

DanUK wrote, "Are polls filled out Anonymously less valid than ones where participants state their name?"

Yes. The latter would be like a petition, which holds more weight than an anonymous poll. If petitions were anonymous, they would have little impact compared to signing your actual name. It's similar to signing a contract saying, "Yes, this is my opinion." Petitions are usually public and people can connect that opinion to your identity. It means more.