Today OFAC designated [http://www.treas.gov/offices/enforcement/ofac/actions/20080710.shtml] two of Makhluf's most visible business enterprises as SDNs - Syriatel and Ramak Duty Free, a chain of duty free stores that includes Damascus Duty Free at the Damascus International Airport. As a result of that designation, U.S. citizens are prohibited from doing business with either entity. (OFAC's press release on the designation can be found at http://www.treas.gov/press/releases/hp1075.htm.)
This may catch many Americans traveling to Syria unaware. The Damascus Duty Free at the airport is reputed [http://www.airlinequality.com/Airports/Airport_forum/dam.htm] to have a large selection of goods at attractive discounts and is popular among travelers departing the airport. The State Department's guidance page [http://travel.state.gov/travel/cis_pa_tw/cis/cis_1035.html] on travel to Syria has not yet been updated to reflect this new restriction, stating only that, because Syria is a designated state sponsor of terrorism, U.S. citizens "are prohibited from engaging in financial transactions which a U.S. person knows or has reasonable cause to believe pose a risk of furthering terrorists' acts in the United States."
Americans traveling in Syria with unlocked GSM phones might also violate the sanctions if they bought a pre-paid SIM card from Syriatel for use in Syria. Buying telcom services from Syriatel is arguably exempt under the Berman Amendment, but the purchase of the hardware - the SIM card - arguably could overstep the line.
One major American company is currently providing service to Syriatel.Network Solutions is the registrar [http://www.networksolutions.com/whois/results.jsp?domain=syriatel.com] for Syriatel.com [http://www.syriatel.com/], which, as of this posting, was still functioning. Given the increased penalties for violating U.S.sanctions laws, it won't be surprising if that site disappears shortly.