Yes, this can certainly be an effective way to learn. There are a lot of tutorial videos out there that show you how to play your favourite song, and being able to go online and find something within seconds is amazing.
The only downside to online lessons is that you don’t have the interaction you sometimes need. If you are not sure of anything during the lesson, then you are not able to ask and get the answer straight away, like you would with one to one tuition.
If you’re learning classical piano, my advice would be to always consider having a tutor for your lessons, but to use any online videos as a second source. I use online videos all the time when I want to learn something new, and I can’t quite figure it out myself.
If you’re learning piano blues, online videos work really well – but I’d advise to follow a modular, progressive course that includes the fundamentals such as techniques.