The Work of Worksheets

Thanks to Dave Mulder and Tamra Dollar for the inspiration and the conversation.
I was cruising my Twitter feeds Friday and came across this tweet from Dave Mulder:

Ooooo…true? RT @TamraDollar: Speaking of "work"sheets...#edchat #colchat #21stedchat #sbgchat #SAMR #pblchat pic.twitter.com/3T3y3e5vZo

— Dave Mulder (@d_mulder) December 6, 2013

Below is the conversation I had around that tweet: I used to assign worksheets in the name of practice.  After all, how else are students going to learn which way water moves when a cell is placed in a hypertonic, hypotonic, and isotonic solution?  How else can they learn to calculate things like density, momentum, and kinetic energy?  They have to practice, right?
Sure they do.  Students have to monitor their progress towards mastering important skills and concepts (and what exactly is important shall be reserved for another blog post).  But if mastering that skill or concept is all you're doing with that particular skill or concept, then the worksheet is busy work.  It's busy teaching students skills and concepts in isolation rather than for a reason, for application....for transfer.  
So, if students can do the worksheet, can they then use the information or skill from it in a meaningful way in a new and unknown situation? (i.e., to solve a problem, create/design a solution)?  If they can't do the worksheet, can they use it to monitor their progress towards skill or concept mastery-and, afterwards, apply their knowledge?  
Like I stated in the conversation above, whether worksheets are good or bad all comes down to the original design and intent of learning. If the design is that the learning stops with the worksheet, then what's the point?  Don't let the only work of worksheets lead students to dead-ended "we're learning this because you need to know this for the next class" or "we're learning this just in case you need it later" learning.