Yes you can unless you have the mat on a thermostat and it is set really really high. Normal heat range is fine. 16 oz cups full of soil are too big/deep for germination and retain far too much moisture for most seeds and young seedlings to tolerate. If you must use it then you only put a couple of inches of soil in it. Then you can add more soil as the plant grows.

Seeds only need a couple of inches to germinate and you get much more effective heating using shallow containers.

Dave

Thanks Dave, thats what i figured. What do you start ur seeds in?

You could use a recycled food container such as margarine,cream cheese,cottage cheese,dips,etc.I germinate my main tomato crop in a Coolwhip container.It is large enough to space seeds with a damp toothpick & can sustain them until I get around to transplanting into 8oz cups.
rose

I use commercial grower's plug trays and six packs since I grow hundreds for sales but the home gardener can use most any thing plastic including all those things rose listed as well as Dixie cups that come in all sorts of sizes, the trays from the salad bar, cut down milk jugs and pop bottles, etc.

Look at the pics in the FAQ here on containers to use.

Dave