I emailed DeWALT about this - here is thier response:
Dear XXXXX, we believe the following information addresses your inquiry.
Memory effect is an old concept, and does not apply to Dewalt batteries.
Please check the following link for Battery "Best practices":
http://www.dewalt.com/us/articles/article_cordless.asp?Site=cordless&ID=702We have been making 14.4v batteries since the early 90's, and they're not going away. Yes, there are considerably more tools in the 18v line, but from a business standpoint, if you consider that over 90% of the cordless tools we sell are 18v, that is why there are more.
Thank you for allowing us the opportunity to serve you. If your question remains unresolved or if you require additional information please update this incident.
Sincerely,