Their sector isn't dead: TUI (which owns Thomson travel among others) is not in trouble. I guess Thomas Cook was already weaker than it should've been (reeling from an ash cloud?) when they were hit by things like lots of North Africa destinations losing their shine.
Not that I know the sector, either as investor or customer!
TUI survived the volcano thing better because they have lots of non-UK operations, especially in Germany, which served routes not effected by the volcano.
In fact there German operations have survived better in General - like the German economy.
A quick reminder to everyone - if you book a holiday, USE A CREDIT CARD. I know you pay a credit card fee, but if anything goes wrong you can be sure of getting your money back.
Also, don't book with Thomas Cook, they're rubbish...