https://bitcointalk.org/index.php?topic=298677.0Bitshares is a ponzi. If something sounds to good to be true (e.g. riskfree interest on your bitcoins), it probably is.
Ignore history at your peril. People bought into pirate to the tune of hundreds of thousands of btc. They were warned by many (including myself) that pirate was most definitely a ponzi. Greed and stupidity triumphed as usual. Look forward to watching the same cycle play out with bitshares.
For details on how the bithsares ponzi operates, see the linked thread at the top.
WARNING: The scam is complicated. You will need an undergrad degree in economics to keep up. If you can't follow the thread, play it safe and don't invest in a 'product' you don't understand. If you can follow the thread, prepare to learn about a complex long con.