The Internet has revolutionized home transcription, no doubt about it. I feel the Internet has probably allowed more transcriptionists to have the confidence to switch to working at home, and more new transcriptionists to be successful working at home than any other single thing I can name.
~ Internet down time ~
You may think "why should I spend my hard-earned money on hard-cover reference materials when I can just look it up online?" Right? While the Internet is an invaluable resource, it should not be your ONLY resource. What if your online service goes down and you can't look anything up for an hour or a day? What do you do then? You go back to the tried and true books!
~ Internet accuracy ~
I trust the hard-copy reference materials to have been thoroughly checked for accuracy and errors (even though an error does slip in now and again). But be aware that the Internet, wonderful as it is, is totally unregulated. Anybody can post anything, and there are no editors checking for accuracy and consistency online like at a publishing house would for a book they are going to publish! You will find many errors in information and spelling on the Internet, and so you must be very careful when using information found on the Internet in your transcribed reports. If I am looking up some obscure bit of information and I find a reference to it on the Internet, I try to always make sure I find at least one more reference (and preferably more) spelled the same way, with the same capitalization, and referring to the same content before I trust using the information in my report.