If you are involved in any type of business that uses the internet, you know how important it is to have redundant internet connections. If one provider goes out or is having access issues, you can quickly go with another provider to keep your internet access looking good.
You can find decent load balancing routers around and they could end up being a very solid purchase if you are doing business online. Another benefit is that two 512k pipes on two separate networks can theoretically deliver more throughput on your computer.