Commodity Hoarding does induce Inflation and it's one of the primary reason of supply side inflationary pressure on economy. Pick any instance of war or political turmoil in any country, you will find inflation ticking up rapidly. So in that case, black money holder as well as formal economic institution would find their net worth eroded which implies that Black money economy cannot act as a cushion for supporting the formal economic institutions rather it will exert more inflationary pressure as these unaccounted money will be harder to control by any measure taken by Govt or RBI.
Now coming on your assertion related to the virtues of black money in Indian economy, there were many analysis carried out by eminent economists around the globe. Links of some are provided here:
http://swaminomics.org/black-money-saves-financial-sector/
http://www.thehindubusinessline.com...e-is-not-a-crisis-in-india/article1622521.ece
Putting all of them together, you may conclude that black money helps us in following ways:
1. In case of collapse of major financial institutions and lending banks, informal lending could be done by black money or in other words liquidity will remain available.
2. Agriculture and rural economy may remain immune due to any economic shock as most of their transactions are unaccounted and not within the tax net.
3. Real Estate prices may not collapse as in the case of 2008 sub prime crisis. Same is the case with gold value; the price of gold may be able to sustain itself on the black money provided the supporting capital is huge.
4. Decrease in operating cost of business due to tax evasion; this may or may not reflect in retail prices but we have to assume that in most of the cases it reduces the retail prices.
5. In case of EMP attack, Black money/Hidden money could save the economy.
There can be many more reasons that you may add but IMO these are the major ones.
Now if you scrutinize the above points you will find significant limitations of black money;
Scrutiny 1: In case of any economic shock or collapse, the credibility of not only the banks & institutions, the value of your currency also sinks as a legal tender of the country. So informal lending will also suffer terribly in that case as well except we start lending and bartering in terms of gold. Even with gold, cost of lending will remain prohibitory high due to high risk involved. So black money or no black money, you are going to sink in both ways when RBI or Big banks go down.
Scrutiny 2: This is partly true. In normal circumstances a self sustaining village economy will not face any major issues but in order to grow and cater its growing population it needs to expand its economic foot print. To do so it needs capital investment for buying tools and fertilizers. As you know informal lending cost is almost double than the formal lending cost( e.g. "2 Takka" or "3 Takka" amounting to 24%-36% annual interest rate) so the benefit of informal lending offsets its benefit. The point is curbing informal lending in black and promoting easy and affordable institutional lending does greater good for rural economy as the cost is low and there may be chances in the event of drought/flood, govt or banks may waive them off completely.
Scrutiny 3: Real Estate prices supported by Black money is always a bane not only for common man but for the whole economy. Unavailability of affordable housing/ manipulation of real estate prices without any underlying basis increases the rental cost leading cost-side inflation push. Low tax revenue from real estate sale leads to low investment in area development and ultimately a big sum of hard earned money goes into pocket of builder-politician nexus to serve their greed and further their economic interests.
Scrutiny 4: It is evident that majority of benefit of tax evasion is passed to scrupulous businessmen and for bribing govt. officials which is contrary to the principle of distribution of profit to the consumer to encourage more buying. Lack of capital investment makes most of our domestically produced goods noncompetitive globally.
Scrutiny 5: EMP attack at its best can target a few server location or satellites. A secured Banking system follows redundant and diverse protective systems with banking data being distributed at various nodes. Moreover, we have many private banks with their own distributed servers so targeting them simultaneously can only break down our economy. But even in that case, what is the guarantee that black money hoarders will come to our rescue. Of course, those hoarding ill-willed cash can't be expected to show good intention while nation is in trouble.
Sorry for the Long post... Please suggest more scenarios in which black money could be beneficial.