It really seems like a bot is constantly buying, like with Mt Gox. But I wonder if that is the case, or it is just general buying pressure from new investors.
It is not a bot and certainly is not a bubble! Bitcoin exchanges can't cope with the number of requests for new registrations by average Joe and Mary just entering cryptoland and buying their first Bitcoin. The avalanche of Bitcoin adoption has just started. It will take years until it settles down.
Edit: Yes, you can say that some exchanges are front running but this is only because they are the first to see organic demand picking up.
New ATH for 'buy Bitcoin' on Google.