Clickable: http://crumbsapp.com/

I think it is a cool idea but that its success will come down to how non-geeks adopt it. If you can get that large pool of non-geeks, whose interaction with the web is dictated by Facebook & Google, to feel incentivized to place notes to their friends then I think it could be a hit. There are also potentially interesting opportunities for local business owners to get 'spontaneous business' via notes placed around their business.

How would you describe your differences from a service like http://geoloqi.com/ ?