The American Embassy in Latvia has posted the following warning:
The American Embassy continues to be concerned about the number of reported instances of crimes perpetrated against foreign clientele at local bars, clubs and lounges in Riga.  There have been a number of additional reports recently of foreign tourists being charged extortionate prices for drinks in bars.  Some have then been assaulted, threatened or forced to withdraw money from an ATM to pay for the bill.   The Regional Security Officer at the American Embassy placed the following establishments off-limits for American staff, their family members and TDY official visitors:
Angels - Elizabetes 22
Babylon (currently closed) - Kaļķu 24; (formerly Roxy Klub) located near the entrance to Old Town on Kaļķu street.
A13 (closed) - Audēju 13; (formerly Mary) located on the east side of Galleria Centrs Mall.
Enigma - Kaļķu 22; located next door to Livu Krodzins. (formerly Puzzle and Pink Panther).
Līvu Krodziņš Bar/Pizzeria - Kaļķu 22 (formerly Royal Pub, Lord's Pub and Groks Pub) located next door to Babylon.
Baltic Saloon – (formerly Red Lion Pub and Saxon) – Laipu 7; located near Livu Square in a small street to the right of restaurant Steiku Haoss.
Golden Dolls (formerly Kapsula Bar and Zephyr Bar) - located on Audeju Iela near Galleria Center in Old Town
Blow Style - formerly Monroe’s nightclub – Skārņu Iela 7, behind Indian Raja.
Hostel Pub - Teātra 12
Sonali Pub - Brīvības 46

These establishments are notorious for credit card fraud extortion scams, prostitution rings and violence by organized criminals. Additionally, several of these bars have begun sending women out to legitimate establishments to lure in clients to other bars, who are then subject to extortion and violence. 
Embassy staff and their family members are officially prohibited from patronizing these locals.  These prohibitions were put into place to ensure the safety of American Embassy employees and their family members.  As noted in the Country Specific Information, these scams can occur at other facilities as well.  All American citizens are reminded to be vigilant to avoid becoming a victim of this type of crime.
The Department of State urges American citizens to take responsibility for their own personal security while traveling overseas.  For general information about appropriate measures travelers can take to protect themselves in an overseas environment, see the Department of State’s “A Safe Trip Abroad.”
If you are the victim of a crime while overseas, in addition to reporting to local police, please contact the nearest U.S. Embassy or Consulate for assistance.  The Embassy or Consulate staff can, for example, assist you to find appropriate medical care, to contact family members or friends and explain how funds could be transferred.  Although the investigation and prosecution of the crime is solely the responsibility of local authorities, consular officers can help you to understand the local criminal justice process and to find an attorney if needed.
In the event of an emergency, The U.S. Embassy in Riga can be reached 24 hours a day, 7 days a week at (+371) 67 03 62 00. The Embassy’s web site, which includes consular information and the most recent messages to the American community in Latvia, is at: riga.usembassy.gov/warden0811.html.