Cartoon animals on YouTube, conspiracy-minded bloggers and sophisticated metals traders are among those to claim JPMorgan is controlling a large part of the world's silver supply.
Some investors contend the US bank's short positions - or bets that the price will fall - have kept the price of silver artificially low.
It may soon be clear whether that was the case. The bank has quietly reduced its large position in the US silver futures market, the Financial Times reportedthis week.
JPMorgan said it was "absolutely incorrect" that it had been pressured by any regulatory agencies to cut back its silver holdings. The US Commodity Futures Trading Commission announced in September 2008 that it was investigating complaints of manipulation in the silver market. It did not specify individual entities, but less than two months ago, Bart Chilton, a member of the commission, said "there have been fraudulent efforts to persuade and deviously control" the price of silver. Such claims have become louder in recent months with the rise in the prices of precious metals.
Silver has gained more than 70 per cent in the past three months, hitting a 30-year high of $30.68 a troy ounce last week.
Silver is often the subject of conspiracy theories, largely because it is seen as a haven asset but also because of its colourful history.
Thirty years ago, the billionaire Texas brothers Nelson Bunker Hunt and Herbert Hunttried to corner the silver market and drove the price up to $50 an ounce. The scheme led to civil conspiracy charges against them.
Whether or not one believes the theories about JPMorgan, in the early afternoon yesterday in London, silver was trading at $29.59, up 3.5 per cent in two days.
There is also the chance that the price has little to do with conspiracies. As with gold, Indian consumers purchase large quantities of silver during the wedding season, and many may be looking at silver as a cheaper alternative this year because of gold's steep rise.
According to the Bombay Bullion Association, India is the world's top buyer of silver, with demand averaging 2,500 tonnes a year.