If the asset is a URL they are accessing, you could pull a webpage report of the number of times someone has accessed that page. If it's gated, you can pull a report on how many times someone filled out that form (provided that the form is unqiue to the asset, otherwise use a filter to specify so).
If the asset is part of a program in Marketo and you are changing program statuses, you can pull a program success report and see how many people achieved success for that asset.