The problem? (I'll assume for the moment you are serious, Greg)

#1.."Finders keepers, losers weepers" is not the same as "I take it, its mine."
'Lost' stuff differs from stolen stuff.

#2.. If you 'take it', you may have NO idea what my situation is. I may be out of work, disabled and even poorer than you. I may seem to have what I need, but have NO means to replace what you take.

#3..If you actually did propose "I take it, its mine." as a valid rule, you would be admitting that I can act on the same rule, and we have a very interesting situation.....do I need to expand the explanation?