Hey Dave,
Thanks for this giveaway, well, the way I look at it is as follows: I know a lot of people are thinking of excluding people with not many posts on the forum such as myself (since some could be 1-post drones for the giveaway) however, there are many of us out there that are pretty active on YouTube comments (like myself). While I might not have signed up for the EEVBlog forum prior to this, I've been pretty much a very active viewer and commenter on YouTube.
With that said, I think the draw should be fairer than that. Since these scopes are VERY expensive, I wouldn't want to give them to somebody who wouldn't have any use for them, it would be such a waste! So perhaps some form of a minimal occupational or academic (degrees) standard should be in place? I have no idea what would be the best way to implement this but I would hate to see a 15K scope wasted on someone who'd never use it!
One way is to have people "tweet" a specific hashtag, and then use a program (or write one) that would filter / pull tweets by Hashtag, then simply randomize a number and pick a winner. You can even filter duplicates so you only count people once no matter how many times they tweet at you. Additionally, the Twitter API allows you to filter by date posted. Therefore, you can make a 48 hour window for people to tweet at you or so, this way people don't spam you forever with the giveaway hashtag.
I'd also be OK with a raffle-style giveaway! $1 tickets, then give the lump-sum to charity or something cool like that (I know a lot of people would disagree with this, but it could be a win-win thing).
All in all, my main concern is that the expensive high-end scopes ending up wasted on someone who's never going to use them, or someone who's just gonna turn around and list them on eBay upon winning.
I hope you have some update for us soon! And hey, thank you so much for this great opportunity! As an electrical and embedded software engineer myself, I know I could REALLY use a high-end scope at home! I mess a lot with Raspberry Pi's, FPGA's and other small computers and a high-end scope would tremendously improve my process!