Not really. Banks were just doing what all good businesses do - make money. 3 x salary is not a rule written down anywhere. Nor does it say that there is any maximum loan to valuation etc. Whether there should be one, mandated by government is another thing. But if you were a bank with access to funds at one interest rate; could lend at a margin; had customers queueing up who would happily go elsewhere; then what exactly would you do? You jump on the bandwagon and let the good times roll.
I'd say it was equally the customer borrowing irresponsibly, and the banks not having enough security. But then not very many UK homes have been repossessed have they?
And yes, government were lending irresponsibly - thats the crux. That there is an EU central bank who sets rates to curb inflation, which was unable to apply the brakes on economies that had sectors growing at many times the official inflation level. Thats a bubble and history is littered with them and their consequences. A major cause of bubbles (away from the public acting like sheep - which is known as "herding") is excess liquidity, which can very easily be tidied up by governments. They dont, because they enjoy riding the wave of prosperity.
So banks act rationally, as they are profit-driven businesses. They act within the rules set by government - in the main.
Governments act rationally, as they wish to be relecected. They enjoy the good times, and accept the moral hazard of bank bailouts.
People act rationally. They see something rising in value and persue it. They neither wish to be left out, nor leave "money on the table". By money on the table, I mean if you see a return of 4% and cash costs you 3%, you do it. Or someone else will.
None of this is new. It has been going on for centuries - Tulips, South Sea Islands (*cough* Darien scheme anyone *cough*). And it will continue. So it is both everyone's fault....and no-ones. Oh, and none of us will ever learn. We will accept speculative bubbles, but will always think we can get out before they burst.
Not for print please.