Maximizing interest income returns

From the stickied post at the top of this blog, you can earn a 5% APY from Insight Visa Prepaid Card (on the first $5,000 balance, up to 4 cards per SSN) and Northpointe Bank Ultimate Checking (on the first $10,000 balance).

With both accounts, you can earn a 5% risk-free return on up to $40,000 of principal. This return beats the pants off of any bond fund in terms of risk-adjusted returns. If you want to take it up even further, you can open 10 Netspend accounts using the same SSN with a 5% APY on the first $1,000 balance for $10,000 (a person from doctorofcredit's comment section reported his total accounts). Account management would not be an issue for individuals in this business as it is assumed that s/he is very organized. I would personally do this with Mint to keep track of balances effortlessly.

Here is a summary

+----------------------+-----------+----------+---------+----------+
| Account              | Interest  | Quantity | Balance | Interest |
+----------------------+-----------+----------+---------+----------+
| Insight Prepaid Card | 5% APY    | 4        | $20,000 | $1000    |
+----------------------+-----------+----------+---------+----------+
| Northpointe Bank     | 5% APY    | 1        | $10,000 | $500     |
| Ultimate Account     |           |          |         |          |
+----------------------+-----------+--------------------+----------+
| Netspend Prepaid Card| 5% APY    | 10       | $10,000 | $500     |
+----------------------+-----------+----------+---------+----------+
| Total                |           |          | $40,000 | $2,000   |
+----------------------+-----------+----------+---------+----------+