The aquatic worm Eunice aphroditois lives in a burrow it will dig for itself at the bottom of 10-40 m deep bodies of warm water. They can grow to over 3 m long and 3 cm diameter, but it typically only exposes no more than a dozen or so centimetres above the seafloor. They're not like a big earthworm, digging through the mud eating whatever organic matter it comes across. Oh, no, they're predatory. E. aphroditois eats coral, other invertebrates and even fish. The mouth is surrounded by five antennae that sense the movement of organisms passing by. When an organism, say a fish, swims by the antennae sense the movement in the water and the worm's quick reflexes take over, snatching its prey with its strong mouth filled with sharp teeth. They typically drag the prey underneath the seafloor into their burrow, inject a toxin, and slowly consume it. Sometimes the snatching motion is so quick and strong E. aphroditois specimens have been known to accidentally rip their prey in half.
I couldn't imagine investing my time so heavily into Facebook that I would consider this "convenient", especially when I can already quite easily electronically transfer money to a friend without Facebook acting as the middleman. Nor would I want Facebook to have my financial information; the thought makes me shudder.
And, of course, if I wanted to give a friend $20 I could just hand them a $20 bill...
When I found out on the local news that there is a program which can measure your big five personality preferences on facebook by analyzing word usage, likes, and posting habits. In addition to, measuring anyone on your freinds list preferences without their consent. I did away with mine.