Hmmm... based on comments posted (by SmartWater employees, no less) in Bruce Schneier's blog, some more thoughts.
It's entirely possible that I may have been confusing two or even three products. In my defense, I was going off the information in the Wired article
and the main product page
of the SmartWater web site, which do not state that the SmartWater product dries/hardens to a point where it will not come off the property in question. The references to "water" and "liquid" would imply the contrary (especially given the existence of a product that is a spray and does *not* harden), but that might just be a marketing or labeling issue.
The Wired article noted above (which I should have referenced in my previous post, my apologies) doesn't even mention the Index Solutions product (which is the spray-at-intrusion stuff) by name, instead naming only the Tracer/Instant products. However, I think my problem with the article is that it (in my opinion) implies that you can get the benefits of the Index Solution (close to guaranteed conviction jail time for the unequivocably identified perp) with the Tracer/Instant products. The Index Solution product isn't even mentioned by name, and yet many of the quotes ("It's practically impossible for a criminal to remove; it stays on skin and clothing for months", "Now, if a suspect caught with a stolen VCR turns green, they can't claim they got it from some bloke down the pub") are actually clearly referring to Index Solution, not the Tracer/Instant products that are the ones mentioned by name.
As another example of potentially misleading data, whether intentional or not, the statement in the article that:
"Word on the criminal grapevine, say police, is that anyone stealing from a coded home is likely to leave the crime scene having pilfered an indelible binary sequence that will lead only to jail time; it's not worth the risk."
seems confusing in the context of the above: the concept of "indelible binary sequence" is true only of the Tracer or Instant products since the spray (Index Solution product) is not "indelible": difficult to remove, yes, but not indelible. And yet the quote claims the benefits ("lead only to jail time") really only applicable to the spray technology, which is not mentioned by name.
I would also state that comments left in Mr. Schneier's blog have made it clear that others are confused by the same issues as well. Again, I make no claim that this confusion is an intended or unintended result, and I am perfectly willing to provide the benefit of the doubt.
Whether it is feasible to have all homeowners install a system that sprays intruders and thus provides all these benefits depends on cost: is it more or less expensive than a similar alarm/notification system, the stickers for which also serve as a significant deterrent? I can't see a spray system being any less expensive, and I can imagine it costing significantly more (just based the cost of sensors, directional nozzles and pressurized containers of fluid located at the right entry points, vs. just sensors and a wire to a central point).
As Mr. Schneier always mentions, it's an equation that takes into account incremental reduction of risk vs. incremental increase in cost, wnere cost *includes* the price but also other has to take into account other effects: on privacy, freedom, anonymity, etc. I suspect homeowners will go with whatever will get them "sufficient" deterrence and protection for a reasonable "cost".
The Wired article mentions SmartWater being given away for free in certain areas, but I had assumed that is the Tracer/Instant product, and not the intruder-marking spray setup. I don't disagree with the concept of this suite of products potentially reducing crime where implemented: I am questioning the cost equation.