What questions about twitter marketing would you most like to have tested?

I'm organizing a small group to perform some twitter experiments, testing different methods and uses of twitter for marketing (and by marketing, I mean contributing to business goals, whether they be PR or click-throughs to content, not sales specifically).

I'm looking to test things like:

• "How effective is using non-event hashtags to get followers?"
• "What words included in a tweet best aid click-through to an included link?"
• "What are the best ways to get someone who follows few people back to follow you?"
• "Does the presence of non-twitter contact info in a twitter page background affect follow-back rates?"

What questions would you most like to see answered?

What gets the greatest number of responses?

1. What affect does shortening a URL (versus not) have on the clickthrough rate? On the RT rate? (Personally, I don't like clicking a link if I can't see the domain. But I'm guessing most people on Twitter aren't security conscious.)
2. What affect does your level of activity have on your follower count? (Some are very chatty (with other folks), some tweet once every hour, some tweet once a day, some tweet once every few days, etc. How does this affect your chances of being followed?)
3. Does having a custom background increase your chances of being followed?
4. How effective are Twitter Chats for gaining followers?
5. Is there a correlation between number of followers and number of RTs?
6. What day of the week gets the most RTs?
7. What day of the week is the busiest, in terms of traffic?
8. What time of the day gets the most RTs?
9. What time of the day is the busiest, in terms of traffic?

I know the last 4 questions have been answered before, but it might be interesting to see if you get the same results.

I'd be interested in seeing your results. Please come back and share them with us!