Please have some idea what it is you are doing and convey it clearly in your post. This was inspired by two fairly recent posts which call into question two well-known vendors.
http://www.reddit.com/r/DarkNetMarkets/comments/2y2kko/psaarticle_recrystalized_stealthbombers_mdma/
http://www.reddit.com/r/DarkNetMarkets/comments/2zbfe2/canadianforger_brown_sugar_acetone_wash/
"Washed 1g with cold anhydrous acetone, got .65, bummer man" is not helpful to anyone and leaves out all sorts of information about the experience of the OP, specific technique, properties of the original versus resultant product (melting point, appearance, reagant test, etc), and why the procedure was even done to begin with. How was the acetone rendered anhydrous? What was the filtering process like?
Performing a purification tek you found online does not mean that all your lost yield was cut, nor does it mean that all the remaining product is pure. Unless you have a compelling reason to perform such steps, you're just wasting time and money and risking losing product.
Let me toss a little knowledge into the bin here:
That said, I believe there is plenty of reason to learn to do a basic anhydrous acetone rinse at the very least, if not learning to recrystallize MDMA from IPA and/or acetone.
Some more shots of MDMA from The Erowid's Rhodium archive:
See what I'm saying?