That about sums in it up- does anyone know?
escheatment to the state
It becomes escheated to the state or an unclaimed property company, like this stuff right here.
Normally the bank will hold it for a set period of time in accordance with state or federal law, but after that passes it just sits as unclaimed monies.
ETA- Damn you Bearflag! 
I should have added, what if you have a significant other, but aren’t married and have no will- would they have the ability to try and contest this and maybe be able to get it instead?
This looks like a job for…Gfactor!
I don’t know bank accounts, but for property I suppose that the unmarried SO may be able to make a claim through probate.
Hmmm…IANAL, but it is my understanding that the probate courts are generally loath to go for escheatment if there is any provable heir or other surviving person with entitlement.
I suspect that in the absence of surviving relatives, one would siply have to prove to the satisfaction of the court that either (1) you as SO have a claim to the bank account (e.g., your paycheck or other identifiable negotiable instruments belonging to you were regularly deposited in it, despite the fact that it ‘belonged’ to your late SO); or (2) it was the deceased’s intent that you be given those funds (dozens of ways that this might be evidentiated.)
Escheatment simply means the state accepts it when nobody else has a valid cliam; it doesn’t have one itself, but is the ‘heir of the heirless’ as the representative of the people generally – something like ‘abandoned property’ falls into the hands of the state after X years.
Finding out there are substantial monies at stake would likely be an heir-raising experience.
If canines could have wills, getting the assets of a formerly vicious dog might make you the heir of the dog that bit you.
I’ll show myself out.
It depends.
Generally speaking, the laws of the state you are residing in when you croak will specify what happens.
In some states (like mine), if there is another name on the account, the money belongs to them. Never goes into probate, not part of the Estate, possession passes automatically. If there is not another name on the account it sits in the bank until someone shows up with an appointment as Executor (or Personal Representative) of the deceased.
Escheatment to the State only occurs after X number of years without activity. And most States provide a way of getting the money back.
Please do. 
In this case, no joint accounts of any kind- all the SO could prove is they resided with the deceased. All the more reason to get a will I guess
Here is the Michigan provision on intestate (estates where there is no will) succession:
http://www.legislature.mi.gov/(S(uwfotl55b1l0tuqwtdv1z53e))/mileg.aspx?page=getObject&objectName=mcl-700-2103
http://www.legislature.mi.gov/(S(uwfotl55b1l0tuqwtdv1z53e))/mileg.aspx?page=getObject&objectName=mcl-700-2105
This provision is pretty typical, and in fact it is found in the Uniform Probate Code Archives & Special Collections • Library • Penn Carey Law , which has been adopted, at least partially, by around 20 states: http://estate.findlaw.com/estate-planning/probate-court-laws/estate-planning-law-state-probate.html
Assets that are subject to survivorship provisions like bank accounts (if they are set up correctly) and real estate (ditto) will not generally pass through the estate.
Jesus, you mean my fucking parents who I have nothing to do with could come in and take money over a SO? What the fuck?
Thanks all, and one more question- does someone actively go out and search for assets of someone who dies- like could I just tell the SO if I die, here’s my bank card, take money out as needed till it runs dry, or would someone make the connection that I’m dead and freeze the account, assuming no one asks them to?
This is probably one of those occasions where it would be useful to specify where in the world you are asking the question from.
Touche- US and A, at the moment Northeast TN.
The intestate succession laws in Texas (and I think other states) provide for property to pass to extended family if you have no immediate family. This would include, typically, your grandparents and their descendants (aunts and uncles, cousins, cousins’ children), or possibly even more distant relatives. I suspect that most people have some family, somewhere, when they die.
Incidentally, distant relatives who inherit property through intestate succession laws are sometimes called “laughing heirs,” in reference to the idea that they laugh all the way to the bank after inheriting property from someone they didn’t even know.
Why not just put the SO on the account? I mean it’s one thing to just not think about it, but if you’re thinking about it, why not do a simple will or put the SO on the account? Then you don’t have to worry about workarounds. The book I linked in my last post has forms.
If you die intestate, yep, that’s quite often what happens. Good reason to get your will made today, no? And my rates are reasonable, too!
(Just kidding, get a lawyer in your jurisdiction to write up your will.)
It’s only one point of data, but when my uncle died, my mother, who was his executor, had to send copies of his death certificate to his bank, so I don’t think that banks are notified when someone dies. Although in a small town, individual bank employees might know.
Like Fir na tine said earlier, if your SO’s name is on the account, it would revert to them. And I think it’s possible to put their name on the account as a beneficiary, so that they don’t have access to the account until you die, but it reverts to them automatically once you do.
Not wanting money to go to disliked relatives is one of the reasons that people write wills and marry. I can think of reasons not to do the second, but not the first. That said, I really need to update my will.