At a local hardware store the battery recycling bin has a sign asking that <i>only</i> 9V batteries be taped since there is a much more likely hazard of their side-by-side terminals being directly shorted from inadvertent contact than for those with polar opposite terminals. The mess and hassle of untaping non-9v batteries for recycling centre workers was the cited reason, so my guess is that the fire risk is seen as much less important than the work required to untape them.
Unless I missed something, there is no mention of the risk. (e.g. what % of house fires are caused by small low voltage/low capacity cells? By what factor do storage interventions reduce that risk?) There is a "Battery Safety" link near the bottom of the page but it's 404.
Assuming you throw out <i>dead</i> batteries, what's the harm in shorting them? (If we're talking normal nonrechargable alkaline batteries. If throwing away a lithium battery I'll definitely verify that the cells are totally dead or protect the terminals.)
This seems marginally useful (tape can be dislodged, and a 1.5V alkaline that is at the end of its service life isn't going to do much anyway). But for Lithium Ion things are a bit different, and for 9V blocks as well because they already have a nice series going there and have handy terminals that allow them to connect to each other (cheap source of HV DC: 10 of those clicked together will give you enough juice to run the high side of an electron tube based amp).<p>Lithium Ion I simply discharge until the protection circuit kicks in, after that they are not quite inert but fairly safe to handle. Usually this happens somewhere between 2.5 and 3 V.