Can my friend and I post our own observations of the same organism?

An iNaturalist observation records an encounter between an individual organism and an observer. 

So if you're hiking with some friends and you stumble across a snake on the trail, it's OK for all of you make your own observation of the snake because you are each recording your own encounter with it. It's best for each person to use their own photo(s) for their own observations. iNaturalist differs from other platforms like eBird in that its primary focus is not recording abundance, so it's not possible to share one observation among multiple accounts.