Hi everyone! I have three quick questions about the autograph sessions at Fanime this year. I've never been to one, but I really want to get Masaya Matsukaze's. 
Glad you're looking forward to seeing him.

1. How early do people usually start (or are allowed to start) lining up for the autograph sessions?
According to this Guest of Honor page: http://www.fanime.com/guests-of-honor/ , you're supposed to ask where to line up if you arrive early. For those of you who have experience with autograph sessions, when would you recommend starting to line up?
If it's similar to how we've done it in previous years (sorry I'm not Autographs staff), there'll be a separate waiting room and we'll bring in a group of people at a time. If someone comes in really really early, they'll likely be put in a new line that is separate from the current line. I think most people start lining up an hour early. Depending on how desperate people are, perhaps earlier. There will be two sessions, one on Saturday and another on Sunday so if you miss out on Saturday's, you'll probably have a good idea of when you should line up for Sunday.
2. Is there a limit to how many people can attend each autograph session?
Since each autograph session is an hour long, I imagine there's a cut-off to how many people staff will allow in line. Have any of you ever been turned away from getting an autograph, and why? Is it usually just a "stay in the line and hope for the best" situation?
Yes. We try to get through as many people as we can in the allotted time but may have to cut off the line if there are too many people waiting when the hour is almost up.
One thing to remember is that
the number of people we can get through depends on the attendees.Please have your item ready to be signed by the time it is your turn. This includes deciding where you want the item signed ahead of time, having the item opened to the page you want signed, etc.
Please take your item and move away after you are done so the next person can have their turn. Too often attendees will stand there after their item has been signed and we have to ask them to please leave. This slows down the line and can cause people to miss out. Please also do not try to engage in conversations with the guest. A short comment or two is fine, but there is not enough time to go back and forth. Needless to say, we cannot entertain requests for posed pictures with guests. A staffer can take a picture of you and the guest as your item is being signed, but we can't stop the line from moving along.
Please don't take offense if you're asked to move or leave. We are just trying to get through as many people as possible. And sorry but no, you cannot have more than one item signed.
**Generic "you"s and "your"s.
3. Is it considered taboo to ask voice actors to sign a Death Note?
Since one of Masaya Matsukaze's most recognized roles is Teru Mikami from Death Note (who also happens to be one of my favorite characters from the series), I was considering bringing a Death Note prop to ask him to sign. Has anyone tried this before, or seen this happen before, and how did it go? For what it's worth, I had a friend who asked Takeshi Obata to sign a Death Note at New York Comic Con two years back, and he was fine with it, but I don't know if it's something that's discouraged in autograph sessions...?
We've allowed fan items such as art and cosplay props signed in the past. It's no problem. ...Though perhaps it would be nice if he can sign on the cover instead of inside the book.

(You can have it signed wherever you want.)
There's really only an issue with licensed goods when it comes to things like CDs or DVDs. We might not turn away unofficial merchandise such as playing cards, but officially licensed goods are definitely preferred.