"No, amateur telescopes would probably not give warning of a small object on collision course with earth, "

Thanks for graciouly ceding the key point.

"but they could monitor known, larger asteroids that professionals don't have the time to bother with,"

Bother with? These will be picked up by the new standard search programs.
That said, it is is good to have venues for amateurs - that's where the specialists of tomorrow will train themselves. Asking what opportunities do we want to provide to and what skills do we want to encourage in young astronomers is certainly an admirable undertaking. BUT it must NEVER be confused with professional fully funded search programs.

"thereby catching unexpected changes in their orbits due to perturbations."
Certainly a good field of study for aspiring astronomers.

"They could also serve as a first line of defense for smaller object, near-earth passes,"

NO, THEY CAN'T. PERIOD. This is in fact exactly where we need to have the most advanced facilities possible. Those "smaller objects" hit the Earth with anywhere from 5KT to 50MT of force, and do so regularly.

...

"Every impactor that has hit the earth probably had many near-misses before it finally connected."

NO. There is this fantasy that is promoted by some that only asteroids impact the Earth. Comets and comet fragments have hit the Earth as well.

"Many small bodies turn up routinely on patrol plates or on other types of searches,"

NEO searches are now done with CCDs and intricate image processing programs

"observers rarely have the time or the interest to follow up on them and it would be nice if they could send an email to an organization that could assign that discovery to an amateur who could then determine if it was a new or a recovered object."

Not a bad idea, if funding is not diverted from the professional search.

"Other possibilities include comets, both existing and relict, which are associated with meteoroid streams."

I also like the idea of amateurs going back to old photographic plates, and going through them - they could certainly help with the digital cataloging of these, and they would thus gain introduction to some of the fine old telescopes, and learn about the history of astronomy. Working on pre-recoveries, as they are called.

"A central clearing house coordinating amateurs could provide a useful auxiliary for any planetoid program."

Yes.

"It could provide alternate observers if the dedicated telescopes were in daylight, or clouded out."

NO. Primary work securing public safety needs to be done by professionals.

"It could match up appropriate telescopes with each object (it is not unheard of for some amateurs to have meter aperture reflectors, often backed up with advanced computers and sophisticated imaging equipment) and process observations for online publication."

Not too bad an idea.

"In addition to amateurs, this program could also be extended to college observatories whose instruments may now be too small for astropysical work, but still suitable for this application. It would allow excellent training for students and give a new lease on life to perfectly useable older instrments now being retired due to budget cuts or light pollution."

exactly - see digitizing old plates and pre-recovery above.

"I would suggest you look up the American Association of Variable Star Observers which conducts similar programs with amateurs. Much of what we know about stellar structure and evolution can be traced back to raw data from routine observations made with backyard instruments."

So that's how the cosmologists self-perpetuated.

"Some good science can be done with small scopes."

No doubt, but finding impactors before they hit is done for reasons other than pure science. I'd like to see the youngsters get some opportunities, and some pocket money if its possible, but this money can't come out of the primaty search budgets.

I don't think you understand ite yet what we're dealing with here. My book "Man and impact in the Americas" is available for $34.95.

This load of laundry is done.