The Baltic state's new law against spreading false financial information has outraged human rights campaigners.
In one of a string of high-profile cases, musician Valters Fridenbergs faced a police investigation after he urged the audience to withdraw their money from two major banks.
He later claimed it was a joke, but the police launched a probe nonetheless.
Security police also arrested an economics lecturer, for "distributing untrue data or news about the conditions of the finance system of the Republic of Latvia''.
The lecturer, Dmitrijs Smirnovs, spent two days behind bars before he was granted bail after agreeing not to flee the country.
Mr Smirnovs' crime was to write a newspaper article urging Latvians not to leave their money in the bank.
He also wrote that keeping savings in the local currency, which is called lats and pegged to the euro, was "very dangerous".
Latvian authorities passed the law last year after a mysterious flurry of mobile phone text messages warned the lat was to be devalued in March 2007.
"This has, undoubtedly, been a highly disproportionate response by the security police, and freedom of expression has been dealt a blow in Latvia because it stifles free expression of opinions in what is a legitimate public debate,'' said Anhelina Kamenska of Latvia's Human Rights Centre.
"It could be likened to cracking a nut with a sledgehammer,'' she said.
Latvia, which broke free from the crumbling Soviet bloc in 1991, had boom years after joining the European Union in 2004.
However, the country of 2.3 million people now faces the deepest recession in the EU.
A string of events have fuelled the local rumour mill.
Earlier this month the government took over the nation's second-largest bank, Parex, after an exodus of deposits. Last month, it turned to the IMF for a rescue package.
The arrests have made economists nervous, with many now extra cautious when commenting on the stability of the lat.
A leading economist told AFP on condition of anonymity that he refuses to discuss currency-related issues publicly.
Political scientist Nils Muiznieks of the University of Latvia said the authorities were "ridiculous''.
"Going after currency speculators and traders is one thing, but when it's an economist and a musician making jokes, it's completely different,'' said Mr Muiznieks.
Subscribe