I see a LOT of customer provided vector art files that are not "vinyl cutter ready" at all.
It's pretty common to get files that have the same letters or other paths duplicated on top of each other numerous times. Pen tool strokes do this a lot. The path offset tool is far better for outlining effects, but is only good for vinyl cutting use if the effect is expanded/flattened. Certain transparency effects can yield duplicate paths, especially if the artwork is exported out to PDF or EPS and brought back into Illustrator again -even with Illustrator editing capability left intact.
A vinyl cutter blade is going to cut wherever it sees a path. And if there are 2, 3, 4 or more of the same path sitting on top of each other the blade is just going to cut them all, even if it means cutting completely through the paper or plastic carrier holding the vinyl. Graphics people accustomed only to making graphics for print or the computer screen just don't think about this sort of issue at all.
Open paths are another problem. Then there's poorly auto-traced artwork where the vector path is rough or even closely follows a pixel grid.
Finally there's those folks who think all it takes to provide a vinyl cutter ready logo is grabbing that low resolution JPEG image they sent you the first time, placing the pixel-based image inside of an Adobe Illustrator, CorelDRAW or PDF document and sending that to you instead.