These are EXCELLENT points. If one searches for ASL lessons on line, there is no shortage of websites. Same with YouTube. So many people with limited knowlege trying to pass themselves off as experts on everything these days, it is hard sometimes to separate them from those who know what they are doing. Anyone, including a fumbling beginner such as myself, can memorize a bunch of signs from a book and make a video. What people don't understand is that these signs do not make a language. The biggest misconception - and one that I used to believe too- is that ASL is just substituting signs for english words - and this is what you see being done in the majority of "expert" instruction available online.
I did a lot of research before choosing the websites I use. I know that it is not the optimal way to learn ASL, but in getting my feet wet, it will do for now until I have the time and money to take a proper class from a fluent in ASL and preferably Deaf teacher. The sites I use are the above mentioned Lifeprint.com and WestwoodASL.com. Both are run by deaf men who are teachers of ASL, one college level, the other high school. They each have a somewhat different approach to teaching. Westwood is not free, but certainly not expensive. The Westwood lessons do not focus on vocabulary at all, but instead throw you right into conversation. Lifeprint does a little of both.
I want to start off on the right foot, treat ASL as the separate-from-English language that it is, and not pick up any bad habits that will be harder to correct later. I also don't want to do any disservice to the language. It deserves respect.