Secondary consequences

Substitutes are everywhere, and the do-not-call list appears to be reviving door-to-door salesmen:

"I think companies are looking for new distribution channels for their products," said Amy Robinson, a spokeswoman for the Direct Selling Association, a Washington, D.C.-based trade group. "Direct selling has traditionally been undervalued by Wall Street, but many realize its strength. It's a niche market, but $28.7 billion in sales last year make it nothing to scoff at."

Here is the full story. No, there does not appear to be a one-for-one substitution, but I'll take an unwanted phone call over a knock on the door anyday. Let's also not forget about spam, which threatens to cripple the use of email, as an additional unwanted substitute.