I'm pretty sure these ads are exactly what they are to maximize click-rate, and therefore to give Paint.NET's author the most money. Very exploitative (with emphasis on exploit).
Then he releases a new version, makes even bigger buttons that lead to even scummier malware, and the cycle repeats.
I get the need to make money off of your hard work, and certainly the guy does a fantastic job on the software, but he's pulling some really shitty tactics to make that money. Why not a lite/pro version setup, or something else above board?