Here's my take on what happened.
You order game on Steam and the Credit card pre-authorization charge went through successfully. Steam then gives you the game as a pre-authorization means the funds were available and Credit card details are correct. Had pre-authorization failed, it either means card details are incorrect or no credit left on the account, in that case Steam would send you a declined notice and no game would be given, that would be then the end of that story.
Later, Steam then goes to do the actual charge, which for some reason failed at their payment processor. In general the actual charge transaction should NEVER fail as the pre-authorization was already approved previously. Steam wrongly views this as a chargeback as in most cases it should never happen. I would assume most weird abnormal at Steam are considered chargebacks due to the evidence presented here in this thread.
Steam could easily prevent this from happening, as from what I understand, (and spoken to a few credit card providers already about it when I tried to do the same thing), is that pre-authorization charges CANNOT be charge-backed period, as no money yet changed hands (due to the actual charge not yet taking place).
Most credit card companies do NOT list pre-authorization charges as they happen on their online details. Ones that do are few and far between. The only way to see that they happen is if some places offer email alerts of real-time transactions, but these almost never show the merchant and usually just the amount, or if it were a foreign transaction. With these companies, the only way to see charges is when they actually POST to your account, and for that to happen, the actual charge transaction has to take place (and not just the pre-auth). With a pre-authorization charge, if the charge transaction doesn't happen within a set time (and this time varies between institutions), the pre-auth then falls off the account. Remember that these pre-authorizations that fall off NEVER end up showing on your current or monthly statement.
Finally, since an actual charge has to happen to do a charge-back, then a failure of actually charging the card after a successful pre-authorization could never be considered a charge-back at all, which is what Valve's system is doing....
Consider the timings of what happened here, between the actual pre-auth and charge attempts, couldn't had been no more than a day... and since the actual charging has to happen to actually POST to your account, not even you could issue a charge-back that fast. Most credit card transactions after they are actually charged, take about 2 days until they POST to your statement, now you can issue the charge-back. Then after you issue your chargeback, you have to wait for the bank or card provider to send you an agreement form that you have to fill out and sign, be it online or fax, which takes another day or 2, that gives them coverage should you be lying about your charge-back in an effort to fraud the system. Then after that, will the actual credit card company BEGIN the chargeback, which can take up to a week to actually show up to Valve.
So what have we learned here, 2 days for charge to post to account, a day for them to send you a declaration form that you are being honest, a day for them to respond to you and then begin the chargeback itself, then up to a week for anything to happen. Thats assuming they work very fast, and remember weekends don't count.
So in other words, this takes so long a process, that Valve's claims of blatantly accusing you of filing a charge-back is so full of hogwash, yet you had your account flagged for suspension probably within a day of buying the game. (I honestly doubt they wait more than a day to do the actual charge, infact its probably a LOT quicker as its an instant sale, most places that ship actual goods do the charge when they finally ship the items out)
I would bet Valve has the same 'delayed' suspension as they do with VAC and cheaters, in an effort to avoid would-be thieves details on what transaction caused it.
Valve are in the wrong completely as they have all the transaction logs and times for proof.
(I know there are minor details I probably messed up on, however most of it is generally sound and proves my point)
Just a quick Google shows me that the actual charge where money finally changes hands is officially known as a the 'settlement'.
Full details here on Wikipedia of course: http://en.wikipedia.org/wiki/Authorization_hold