The meaning of the word might have changed, but I do tend to think we the word has always meant, "keeping too much."
But here are my top three times when it's OK to "hoard."
1. You are a squirrel (scrub jay, marmot, pika, rat, etc.) and you need to store food for the winter in order to survive. Even if there is "extra" when spring comes, at least it has padded your lair and insulated it.
2. You live in California (earthquakes), the midwest (tornadoes), a river delta (flooding) or the East (hurricanes and snow storms) and you have created an emergency preparedness kit so you have a better chance of surviving one of these disasters.
The next group I do tend to think of as a little "crazy" but I do harbor a little envy at the same time...
3. You are a "Dooms-dayer" that believes something is coming (an apocalypse, Commies, hippies or Democrats/Republicans) that will change the face of the earth forever and you will need supplies for 6 months or longer and the ability to be self-sufficient after that.
Group 1 is acting on instinct. Something tells them to gather food in order to live.
Groups 2 and 3 might be acting on either real or imagined future scenarios, but both are acting in an organized fashion and are doing what they can get to make sure they can get to their supplies and make use of them when they will need them.
Someone who is keeping things "for the future" or "when I might need them" and is not organized about it, is fooling him/herself into thinking they are just being prepared or frugal.
If you have so much stuff in your home that you can no longer do some basic things (mentioned above--sleep in your bed, sit on your couch, cook in your kitchen, use your bath or shower) because of the things that are piled on your bed, laying on your couch, "stored" in your kitchen or in your stove or piled in your tub or shower, then you have a problem called hoarding.
It may also be preventing you from seeing your family, or your own family from having friends over. It may have ruined a relationship. And it can kill you. (It can prevent emergency personnel from reaching you and even kill you directly if a pile falls on you or trips you up.)
If you are living like this, or know someone who is, please, please, let someone else know. Start seeing a therapist or counselor. Reach out to a friend.
There might be a "Hoarding Task Force" or alliance of some kind in your county or city.
Here are a few resources to start with.
A local mental health agency.
In the San Francisco Bay Area, try:
San Francisco Mental Health Association Institute on Hoarding and Cluttering, http://mha-sf.org/programs/ichc.cfm
National Study Group on Chronic Disorganization, www.nsgcd.org
They provide free Fact Sheets as well as a referral service to help you find a professional organizer trained in helping clients with hoarding issues.
National Association of Professional Organizers, www.napo.net
You can find an organizer in your area. Just be sure s/he lists severe clutter or hoarding as a specialty.
I Care Village, www.icarevillage.com
A new comprehensive online resource for caregivers of the elderly. A section on hoarding is included.
Children of Hoarders website
Comprehensive website with links to local resources, legal advice, therapists in your part of the country. Personal stories, pictures, videos. Not for the faint of heart–but you will realize you are not alone! http://www.childrenofhoarders.com
OCD Foundation (Hoarding Center)
This site is co-edited by Drs. Randy Frost and Gail Skeketee, authors (with David Tolin) of Buried in Treasures (see below). They are on the front line of research into hoarding behaviors. http://www.ocfoundation.info/hoarding/
Buried in Treasures: Help for Compulsive Acquiring, Saving and Hoarding, by David Tolin, Randy Frost and Gail Steketee.