I am curious to see how large the largest completed tournament is?
As well as the largest tournament in actively in progress? /How long has it been playing for?

This has 256 people: http://warlight.net/MultiPlayer.aspx?TournamentID=1215

It started at 256, only 11 remain at the moment.

I'm really bummed I let myself get autobooted from a winning position in the round of 16 of this one.

This one has even got double elimination:
http://warlight.net/MultiPlayer.aspx?TournamentID=551

Incidentally, I'd like to see some new features for large tournaments. The autoboot helps but what about force joins? Can force joins happen automatically after a certain period, like 20 days?
Also, it would be easier to start them if tournament invites that weren't replied to were removed after three days. And, when you invite a large number of people at once, it should invite the number of players it can, rather than inviting none at all when it's over the limit. Alternatively, we should be told how many people we can invite if we go over the limit, because otherwise we have to guess, and it takes forever.

|> The autoboot helps but what about force joins? Can force joins happen automatically after a certain period, like 20 days?

They already do! Once the autoboot timer is reached, they're auto-joined.

|> Also, it would be easier to start them if tournament invites that weren't replied to were removed after three days.

What would that accomplish? Someone who hasn't accepted your tournament doesn't hamper it in any way, except maybe the load time of the tournament screen. This is also a bad experience for the player who sees the tournament invite email late and goes to join, just to find out they didn't act in time. It's not uncommon for a tournament to take more than 3 days to start, so this is a frequent use case.

|> And, when you invite a large number of people at once, it should invite the number of players it can, rather than inviting none at all when it's over the limit.

How would it know who to invite and who to axe? I don't think there's any heuristic here that will satisfy everyone. These kind of decisions are better off put in the player's control.

|> Alternatively, we should be told how many people we can invite if we go over the limit, because otherwise we have to guess, and it takes forever.

The maximum number of invites is 3 times the size of the tournament.

Also, some of your invite limit experiences may have come from round robin tournaments. Prior to 1.4, round robin tournament invites were limited to 1x the size of the tournament.

With the introduction of the round robin size limit in 1.4, this restriction has been lifted. Round robin tournaments now allow invites up to 3x the tournament sizes just like single-elimination and double-elimination.

Because lots of people never reply, so by removing them more (active) players can be invited? Am I missing something there? Players could be re-invited if they see the invite late.

Would it cause problems in some cases if it just invited the people at the top of the list?

I wasn't aware what determined the maximum number of invites, but even so, it would be far easier to be told how many more people we could invite than to have to calculate it.

That's good to know about the force joins, but there are a few stalled pre-autoboot tournaments I'm in.