Ask HN: An employee at a competitor signs up to your site. What do you do?

Background: The first competitor in this space started back in 2012. I had a look at their product last year and thought I could do better.

For the last year, my product has been a sub-set of their features with a better UI/UX (in my opinion anyway!). I recently started to differentiate though and released a feature they don't have and am working on releasing other new/differentiated features.

Other background: They're definitely the biggest in this space, but recently, they've been losing a lot of customers to a different competitor that started in 2014, but they don't seem to have copied any of the differentiated features that competitor has released (yet).

Today, I saw that someone from their company signed up to my site. They only have ~10 employees, so they definitely know I exist now.

Is there anything that you would do in this situation, or just keep moving along?