I agree with this text because when you use the Internet it's so easy that other people see your e-mails, conversations,... In the e-mails the people don't see your face and neither hear your voice, so, they maybe don't understand what you mean.
It's easy use abbreviations because you write faster, but sometimes you must write corretly, for example, when you write an e-mail for a teacher, because maybe there is an important matter. If you talk with your friends, you will write with abbreviations because they understand you.
In the end, you must be careful what you write on the Internet