COLUMBIA, Md.--(BUSINESS WIRE)--Merkle (www.merkleinc.com), a leading technology-enabled, data-driven performance marketing agency, announced the appointment of two senior members to its Retail & Consumer Goods practice: Mark Guenther, vice president and Alex Kooluris, vice president. Mark Guenther’s direct marketing career has spanned over 19 years, including his eight-year tenure with Merkle. In response to the agency’s immense and diverse performance marketing opportunity within the reta