When an investment become successful, many companies will try to sell it. I seen many ads everyday in Google ads, Facebook ads and even local classified websites showing thousands of successful cases and asking you to invest in Bitcoin.
This is normal I guess.
That's bit different because Google and Facebook know that you are intrested in bitcoins so they target those adds to you. In my opinion, underground is more mainstream. I saw them on Jubilee line stations London Bridge and Canary Wharf (big screens there), by the way.