Venting and explosions are fortunately very rare events; so rare they usually make the news despite there being hundreds of millions (billions?) of lithium batteries in service. Just about every electronic device you own has a lithium battery in it. Your phone, your tablet, your laptop, your calculator, your hearing aid, your wristwatch, your iPod, you name it. If you have a desktop computer, it has a lithium battery in it to keep the clock running so you don't have to reset the time every time you turn it off or unplug it. In almost all cases, a vent or explosion involves a damaged battery, or improper usage or storage or charging. E-cigs are particularly prone to such abuse because the users of these devices have a lot more control over how the battery is used than in most other applications-- you can't, for example, put too low a coil in your cell phone-- because the battery in many e-cigs is removable, and because the amp draw in e-cigs is normally a lot greater than in other electronic devices. The battery pack in your cordless drill has to withstand a lot of power usage but, even in a small one, it usually has 4 or more cells to divide the load.
All that said, under most circumstances, a battery will get very hot before a vent or explosion. Unfortunately, sometimes it can occur so fast the heat doesn't have time to make itself known before the damage is done. This normally occurs in the case of a dead short, in the case of an e-cig, and sometimes by a physical shock to the battery while it is charging, when it is unstable. That last can occur to any kind of lithium battery by, for example, knocking you cell off the table onto a hard floor while it's plugged in. A vent or explosion can also occur to any kind of lithium battery if the battery casing is damaged or torn or punctured. I repeat, though, this is unlikely to occur to anyone who understands battery safety and treats their batteries with the respect due such a large amount of power crammed into such a small space.