It wasn't until Napster made that 0 minutes of googling that MP3 filesharing really took off.
For something like this to end up on millions of desktops, you have to be able to explain it to a half-stoned frat at a party. "Five minutes of googling and then some nerdery"? No chance. "Install this, go to the quad and you can sign into the facebook of any other person there?" Yup, that's going to spread like wildfire.
This isn't new. Point and click tools for doing this existed 10 years ago. Making a firefox plugin just pushed it back to the top of the headlines. This is actually a good thing because if word spreads more people will be aware of the already existing risk and will be more security conscious.
Does this mean everyone should stop logging into their personal accounts over unsecure wifi at school or starbucks? ABSOLUTELY.
Hopefully this new attention on an old hole will motivate more admins to fix their networks and more users to realize how vulnerable they are.
(a) network effects
(b) autosharing, spurring more (a)
Neither of these apply here.