Bitcoins and script mining

[scole of TSBT]

Companies are selling ASIC devices to do Bitcoin mining. Based on the current value of Bitcoins and the device’s hash rate, these devices appear to be able to pay for themselves in 2-3 months. Are these devices worth considering? Sounds too good to be true. Are the companies taking your money and never delivering product or do these devices simply not mine at a rate that makes that money back? I understand that the difficulty level for all script mining is increasing. Are these devices already obsolete?

[Silver]

From the limited amount that I know about mining I have to say I'm not quite convinced how it can all work and more importantly what's to stop it all disappearing one day? The recent collapse of the MtGox exchange does nothing to reassure me that if I bought some gear and mined that my 'money' couldn't/wouldn't disappear or be worthless.

The Asic units were promised for a long time and I think there were people lost out on machines/cards that were never delivered and some 'companies' vanished but the gear is now real. I think asic is the 'current device' its gpu's that are now almost obsolete for mining owing to the increased difficulty - something else I don't really understand but haven't really looked into properly

[Megacruncher]

From the limited amount that I know about mining I have to say I'm not quite convinced how it can all work and more importantly what's to stop it all disappearing one day?

To be fair this is the problem with currency. Whether it's cowrie shells, gold, the Papiermark or Zimbabwean Dollar, it only works afor as long as people believe in it.

I have to say that last time I looked at bit-mining the consensus seemed to be that there were too many miners chasing too few bit coins for it to be worth the cost of the 'lecky.

[scole of TSBT]

There's still about 9,000,000 of the 21,000,000 total bitcoins left to be mined. I'm still trying to understand the difficulty level thing. Is the difficulty level simply the progression in the number of calculations required to find the next hash or are artificial constraints being imposed to keep the number of new bitcoins mined down?