Ask HN: What's with the one-off usernames?

As asked by krubner on this post http://news.ycombinator.com/item?id=4490159 submitted by "onetimeuse001", what is the cultural or psychological meaning of these one-time-use usernames on Hacker News? What purpose do they serve (other than to mask long-term users for reasons unknown)? It would be one thing if someone wanted to answer a sensitive thread anonymously, or even post off-topic content that one finds intellectually important, but is that what is really going on? A lot more green handles seem to be appearing on HN lately, many of which are decidedly for one-time usage. Any ideas?