I think that the title means that writing text it is not as interchangeable as digital text. If you write it down on paper, then you have to use an eraser or start over from scratch, or mail it to someone if you want them to see it.
Web 2.0 affects someone who is ready to enter the workforce because they will most likely be forced to use this type of system to communicate ideas and thoughts back and forth using software such as this.
It affects people who are already in the workforce in the way that they are going to have to learn this new way of communication if they are going to want to be fluent in the language that the "newbies are using" to communicate.
When they say that we will have to rethink everything, they mean that we are going to have to open our minds up to communicating in a new and unfamiliar type of setting.