There aren't many ways to connect to the internet. At home there are two ways, directly to your cable modem or DSL modem and to a router that's connected to your cable modem or DSL modem. So should one spend the extra money on a router or not?
Yes, spend the extra money on a router. This is especially important for Windows users, but Mac users should be cautious as well.
Malicious Internet attacks happen all day long, and not just from an email or a spoofing website. There are attackers out there that scan ISP nodes all day long for IP addresses, Internet traffic, any kind of activity. These are the people that can get hold of your personal information without even being in the same area.
The best way to prevent these types of intrusions is to purchase a router and install it directly to your ISP supplied modem. The next step is to READ THE INSTRUCTIONS! Installing a router doesn't do much unless it's configured for security.
Most router manufactures post their manuals on the web. If users don't configure the security settings, like changing administration passwords, they're sitting ducks for an attack.
Erik