That is a good choice. Find someone who has something to sell or market such as a book, an album, a film, or someone who has important research they want to discuss. You can approach them by offering them an audience which to an artist or writer nothing can be more important. You don't have to give them anything except the opportunity to introduce themselves on a new forum. Chances are they want to improve their Qscore if they know what it is and if they don't then why not tell them? Then of course Steem benefits from it too. I also know Qscore isn't the only metric but Klout and others exist so any metrics can improve things for both the artist and Steem.

early facebook was edu only...it works

He is an advisor on a competitor.

This is exactly the wrong approach. Don't approach with a request for money. Ask for an Interview such as an AMA and don't ask for anything but that which a journalist would ask for. Let them talk about their book or sell their new movie. And don't approach based on Time.com but instead on Qscore. Some people who have a high Qscore are not obvious celebrities and might not even know they have a high Qscore while a person who knows they are a person of influence might have an ego and be different to deal with.

Why Snowden? Does Snowden have a high Qscore? If there is no quantifiable reason to approach someone then maybe you shouldn't approach them and ideology in my opinion is one of the worst possible reasons to approach celebrities if you're trying to build a mainstream community. If you want to build a community of Snowden supporters then if Snowden and other highly controversial political figures post here then you could attract a certain demographic but at the same time if you get too much of that demographic early on it could keep other demographics from ever giving Steem a chance.

The best approach is to go with Qscore and polls. If the Qscore is high then seek them for an AMA or interview of some sort. Do not talk about the tech or the investment. All they need to know is that Steem is a more advanced newer kind of Reddit platform. Let them find out the features on their own or if they ask. 

If you go with polls then just poll the community and ask "who on this list of high Qscore celebrities, companies, should Steem associate itself with?". That way you get input from the community but at the same time you only choose people with a high enough score to improve the brand. If necessary give surveys to the community to figure out the initial demographics so you can at least know when demographics change from early adopter to something more mainstream. In theory you could reward everyone who proves they took the survey with up votes.