Roger sockpuppets will think this is a scam because it's hosted on Luke's website.
I can't see anyone saying that it's a "scam", that seems like a straw man.
It's obviously a legitimate poll, however it may be
subject to biases because it's hosted on Luke's website, in the same way that Bitcoin.com's polls are subject to biases because they're hosted on Roger Ver's site (and their polls support block size increases). No poll can promise to be 100% neutral but, hosted by people who are biased, we should be careful about trusting the results.
There's also the fact that we're talking about ~100 answers here, and that those answers could be from
anyone, so if you're someone influential who strongly supports one side, you won't find it particularly hard to find 100 people or so to say that they agree with what you say.
2. Do you have any way to know which sites/portals the respondents came from? (i.e., breakdown of r/bitcoin vs. r/btc)
Ideally, you would stratify the samples based on this.
First you pick a sample size - let's say 1,000. Find out how many readers r/Bitcoin has (about 258,000), how many readers r/btc has (about 45,000), and how many active readers Bitcointalk has (people who have been logged in within x amount of time). If you can find other places, include them. Then you choose the number of readers to ask from each place based on how many users there are.
Then you use a random number generator to find random users from each place, depending on how many people use each place.
Then you have a neutral and accurate poll.