The Data Acquisition System at the Free-Electron-Laser Hamburg (FLASH) has evolved since its implementation in 2005 into a reliable and versatile system used for accelerator operations and studies along with a multitude of different photon experiment users, recording about 14 TB in 2008 for experiments only. Recently the DAQ system has been successfully upgraded with new hardware to accommodate increasing demands of beamline experiments, upcoming R&D work at FLASH i.e. for the ILC, and to prepare for the upgrade of the FLASH facility this year. The design of the FLASH DAQ is based on a very scalable and extensible concept, recording all available data, processing and archiving it as well as providing an interface for the user to analyze their measurements. Several instances of the same DAQ system have been installed now in parallel to the existing ones to allow for a flexible and redundant configuration, adjusted to the needs of the different user communities. This paper describes the evolution of and experiences with the FLASH DAQ and highlights the key elements of its design to facilitate an expandable yet easily to duplicate system implementation.