My apologies for suggesting 'its' is a plural possessive pronoun rather than a possessive form of 'it'. What can I say - it's very late. It's lucky I mentioned that I'm a layman, not a scholar.

@nigel.pindar: Your example of the difference between its and it's is erroneous. It sounds possesive writing 'its mine', but it's obviously incorrect as, in this case, it means 'it is mine' - it's being the correct usage as a contraction of 'it is'. 'Its' is the plural possessive pronoun of it (obviously). It's plain to see that the dog does not like sharing its bone. Not a great sentence, but one which hopefully makes it clearer.
An interesting forum, with many well informed contributers. I am in no way of the same calibre, and do not pretend to be, but perhaps the discussions on some subjects here have gone on for far too long. They are, in the end, fairly trivial. The English language is a wonderful thing, full of surprises and quirks and is made all the richer by subtle changes. Sticking solely to the past is retrogressive by its very nature, and does not allow for fresh life to be breathed into it. Latin and Greek are dead languages, but they are still very much alive, in part, within our wonderful language. Academics,it seems to me, spend way too much time considering the minutia to be able to see the bigger picture. I cannot see that using 'forums' instead of 'fora' is, in some way, a great insult to the English language. I see it, rather, as growth. If there are any grammatical errors in my posting, so be it, but I won't lose too much sleep over it. I will, however, as a layman, try to improve my understanding of my mother tongue. Now, who was it who said in an earlier post that WTF is an acronym rather than an initialism? Just joking!