Thoughts on Giveaways?

A big part of my channel is giving stuff away through a random online draw (It's called Geek Raffles so it's kind of in the name...). A small one every week or two and a bigger one for milestones like 100 subscribers. I'm hoping this will be a decent way to get someone to subscribe if they happen to come across my channel. Thoughts? Has anyone done something similar and had decent results?