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That service supports many projections (see the section of the capabilities with the comment "All supported EPSG projections:") including 3857, which is equivalent to 102100.
Try:
<layer label="Marine" type="wms" visible="true"
url="http://cmgds.marine.usgs.gov/geoserver/track/ows"
skipgetcapabilities="true" wkid="3857"
visiblelayers="lidar"/>
Does ArcGIS Viewer for Flex support identify WMS layers?
No, identify on WMS is not supported in neither the Flex API, nor the Flex Viewer.
FYI - That link requires people to log in to salesforce.