I don't know if you've seen this thread before, but the longest losing streak at 49.5% on Just-Dice back when we accepted Bitcoin was 32:

  https://bitcointalk.org/index.php?topic=610339.msg7060900#msg7060900

Interestingly, the 2nd longest was 5 bets shorter, at 27.

I would be interested to know if anyone has ever seen a longer losing streak at 49.5% than 32 in a row.

Roughly speaking, the odds against 10 in a row is one in a thousand, 20 in a row is one in a million, and 30 in a row is one in a billion.

So that 32 in a row is a one in four billion shot. The losing streak ended with bet number 594,791,171 and that counter includes all bets, not just those at 49.5%.

Edit: here's a screenshot of the 27-streak: