Why does getting a 2-5% yield for what you admit is a very risky investment seem compelling to you?
According to Bloomberg, investment grade corporate bonds (a safe investment) are currently yielding 3.52%, and high yield bonds are currently yielding 5.97%.[1]
You can buy an ETF (ticker: JNK) that has a diversified portfolio of high yield bonds that yields 5.84%.[2]
By failing to list such investment alternatives on its web site, solarcity.com is making their bonds look like a deceptively good investment. Sure, it's easy to beat high yield CD rates, but CDs have no capital risk (bank accounts are FDIC insured).
[1] http://www.bloomberg.com/markets/rates-bonds/corporate-bonds...