Is the junk really that - junk? Or is it "junk" in terms of being comprised of items that were placed into orbit that are no longer able to perform their initial duties?

Is this junk really so value-less that pushing it into the atmosphere (for what I presume to be disintegration during re-entry) is the best solution? Is collecting the junk a more expensive proposition than retrieving it and returning it to Earth for recycling and/or repurposing?

If I remember my RAH young adult novels correctly, having the scow vessel travelling in a higher orbit means it travels faster then the majority of the junk it's to collect. If that's so then Cringely's purse-seine net idea is actually much more economical then a 'bot device for each object such as you suggest Stephen (except for the largest items). I do wonder if tossing it all back into the atmosphere to burn up is the best option though. We (somebody) already spent oddles getting the stuff into orbit in the first place, isn't there some better on orbit use this material could be put to once it has been secured? Seems a pity to literally waste the lift investment each item represents. Since the suggested scow design appears to be tele-operated from the planetary surface, why couldn't it (scow and recovered material together) be ultimately transferred to a higher orbit still and used as an on orbit general hardware resource that periodically makes a multi-orbital pass to "re-stock" from the remaining stray assets clogging up NEO regions?

Presenting Nanotech Scrubbing Bubbles: They work hard at keeping space sparkling clean so astronauts won't have to.

I fail to see why a bot that missed an intended target would throw itself into the atmosphere.

Apparently the idea is that the bot would ram the target and send it into the atmosphere like a billiard ball.

I visualize it more like this:

The bot approaches from behind and snares the target in a net. Then it adjusts course slightly and goes after another piece of debris.

At some point, depending upon the mass collected, the bot and debris could reentr the atmosphere over the Pacific.

But bots are going to be expensive, so probably they should detach only the net and contents and send that down to its doom.

Bots could visit a space station for refueling and refitting or wait to be visited by astronauts to do that.

Going after multiple targets may be tricky because these are in wildly different orbits. The best case are pieces from a single launch because they're going to be on reasonably close trajectories but the longer they've been up there the greater the dispersion due to tidal forces. You are not going to collect garbage in polar orbit in the same mission as a geosyncronous pickup.

Depending on the size and location some junk may not need to be physically intercepted. Turn a 100MW laser on a 1 kg piece of scrap metal and no one will notice the resulting cloud of plasma even if they run straight into it. Some Larger bits can be "nudged" into the atmosphere by judicious application of laser fire from high orbit. Some is just going to have to be manually collected and dealt with directly.