When you think about threats to Hewlett-Packard's bottom line, you have to consider Daniel Wencel.
He and 20-year-old son Chris have created a new franchise, dubbed Caboodle Cartridge, that refills old ink-jet and laser printer cartridges for about half the price of a new cartridge.
This kind of small business ordinarily wouldn't catch the eye of Palo Alto-based HP, which reported $73.7 billion in revenue for its last fiscal year.
But 70 percent of HP's operating profit comes from its imaging and printing division, and most of that profit, analysts say, is from selling replacement ink-jet and laser printer supplies. If Caboodle and other businesses like it catch on, they could put a dent in HP's profit machine.