In an answer of mine for the question '[Who are all the characters to have touched The One Ring?](https://scifi.stackexchange.com/questions/31610/who-are-all-the-characters-to-have-touched-the-one-ring/31611#31611)', [someone](https://scifi.stackexchange.com/users/1801/lamwaiman1988) astutely asked 'how come?'

Was Gandalf aware of the Rings' effects on a holder before burdening Frodo with it? And while 'hidden', it [did](http://en.wikipedia.org/wiki/Frodo_Baggins#Characteristics_and_appearance) have some obvious effects during those 17 years, not the least of which was not appearing to have unnaturally-aged since receiving it.