A BOB is a bug-out-bag, typically containing enough gear to get you to a predesignated safe place where you have a larger cache (or to get you home) - it usually contains a minimum of three days worth of food and water and enough gear to get you there in relative safety and comfort. It is assembled based on your needs (urban, suburban, rural) and it really doesn't cost a lot of money to have on hand. If you think you don't need one, think back to NYC during the blackouts or after 9/11. Those that had their BOB in their car or at their desks were better equipped to bug out to get home - and they were MUCH more comfortable.
An INCH is an "I'm never coming home" again bag. This bag (or collection of bags) is where a lot of people go overboard and yes, it can require a significant investment. I have seen INCH bags that have enough well thought out equipment to start a small village after the zombie Apocalypse. INCH bags are not nearly as common and usually only undertaken by avid outdoors lovers that really get into this endeavor as a hobby - or they seriously think the S#@! is going to hit the fan . . . there are even contests to go out and use your INCH bag for months at a time to see who might have the best chance based on what they've taken. Many people would rather just eat a bullet than to build and comprehend (and face the prospect of using) what goes into a REAL INCH bag . . . if a collapse of that magnitude happens, a lot of people surveyed have said they would consider themselves to be better off dead.
Myself, I'm lucky enough to have the disposable income to put together several bags, and even help others build their own. I have different BOBs for different scenarios and INCH bags that would rival what our government probably has in place for our military.
For me, it turned into a hobby, I began just browsing survival Websites and my family was always ready with some type of plan, it seemed fun. I've actually won a three month INCH contest in Montana that traversed winter / spring. That was my kind of fun . . . I know it isn't everyone's cup of tea, but hey, it keeps me out of the wife's hair. And sometimes, that's priceless.
Due to the construction of this bag and the features, many people would consider this bag to actually be a shoulder mountable rucksack. Traditionally (colloquially), most people consider a rucksack to be just like this, an enclosed top-only load bag - which is why I mentioned that IMHO this is a good addition to a BOB or INCH, but not a primary carry bag for that purpose. Although, for MOST people, this would make the beginnings of a VERY DECENT BOB. And SOMETHING is better than NOTHING. It is after all, a very durable bag and it performs very well!
This bag and the "ten essentials" - http://en.wikipedia.org/wiki/Ten_Essentials plus a few extra items would suit 95% or more people VERY WELL - and it will all fit in this bag, and doing it (buying a bag such as this and building a simple BOB) will possibly save your life.