Here's some middle of the road fence straddling comments from me.

For those lucky very few people with an ancient camp on their private property, they obviously make their own decision on hand dig or power
excavate.

But for the masses of amateur collectors, hand dig or screen is just a matter of what is available to them if they want to grow their collections.

After the first couple of months, pay hand digs become a nice intense exercise day in the great outdoors moving someone elses' old dirt. Still worthwhile vs zero finds sitting at home watching TV.

Power screening a viable mound is the land owners perogative on how he wants to deal with having strangers on his property. The central area of a mound can be very productive as at the present Juno site then get "slow" where hand digging would be non productive..

In favor of power screen digging consider the Nacho Barksdale site that is so well known over the last FIVE YEARS.. It's about a half mile long all
along the highest bank of the Nueces river.
That was not a " camp " a half mile long but rather many firerock midden camps with a barren space between.
It's unthinkable that even a troop of hand diggers would ever be able to carefully move 2500 X 200 X 6 feet deep.

There have been 5 full years of absolute treasures gleaned by power screening between camps that might have been covered over by future " land
developers " ( indeed the present owner had it platted out for ranchettes )

How about a compromise...serious diggers like Travis 1 have made their own
small power vibrating screen, just hand dig / load the screen !
.
.

?

All right !! Now I got some good opinions on a contraversial subject. I think there are certain benefits to power equipment on arch sites like, take off the top couple of feet of sand or clay. Also certain point types and blades are much hardier just as they were made thicker or more rugged. Not damaged as easily as the fine stuff. You can't tell me that needle tips and delicate ears and power equipment are EVER a good mix...A wiggle pick and concrete camp bottom are tricky enough. When you see bone beads and shell Gorgets come out two or three feet down mixed with rock you thank the lord you didn't stick your pick through one or find the pieces on a screen table. My point was not how many you find by moving acres of dirt. Some areas along the Nueces should have been designated (hand dig only) IMO but like you said Hal there's a ranchette on it now... If your in no hurry and you have access that is not going away in the near future, don't let people pot hole it. Study it as you pick it apart learn the layers and make an informed decision to use power equipmet to clear the top or clean out back dirt to expose un-dug areas.
Filling a frame is fun but the knowledge of how the Natives functioned is priceless.
Be a guardian to the areas you have access to and you will be rewarded.