Often they're an old, well-known form of scam.
In most personal injury suits you pay no up-front attorney fees, instead they get a healthy percentage if you win. If you lose no cost to you.
In these stock class-action suits, they'll ask you to pay up front. As long as they never ask for any $$$$, you're cool.
All that is needed to make a happy life is within yourself, in your way of thinking. -Marcus Aurelius