Recently I came across the statement:

"Unarguably, the best source for learning signs is to learn them directly from members of the Deaf Community."

That seems like really good advice.

However I want you to consider that statement carefully:
"Unarguably, the best source for learning signs is to learn them directly from members of the Deaf Community."

For "fun" I'm going to argue. (Heh). (Forgive me.)

Suppose I said to you, "The best source for learning English is your neighbor, Joe the plumber."  Or "Donald Trump." 
Would you be inclined to agree? 

I'm not convinced that "the best" source for learning a language consists of random "members" of the community that speak that language.  If so, you are going to have a lot of people running around saying "Yuuuge!" (in a Queens, New York accent).

The above being said, yes, of course the statement makes an important point in general:  ASL students need to interact with the Deaf community.

But why -- really?

Often "in real life" Deaf community members include in their signing a mix-mash of Signed English, sloppy signing, and regional signs.  If ASL teachers are not teaching those, ahem, "other" signing styles then students are only going to pick up "real life signing" by interacting with the Deaf community. 

Students should indeed interact with the Deaf community -- but not so they can learn textbook ASL signs.  Rather students should interact with Deaf people in order to learn the many non-ASL signs (such as VERY, AND, BECAUSE, BREAKFAST, etc.) and alternate forms of signs that form the undercurrent of communication within the Deaf world or what you might call "real life signing" as done by Deaf people in everyday communication situations.

Students become powerful communicators by combining their knowledge of formal ASL (acquired via formal class, video, and book learning) along with real life "signing" (not necessarily ASL but indeed what is appearing on the hands of many Deaf community members) via interacting with the Deaf community.

- Dr. Bill