Why - do you think only people/companies who are rich should be able to bring lawsuits ?

The availability of litigation financing to people with legitimate legal complaints is critical to having a fair legal system.

Is this a reasonable vehicle for entities that simply would not otherwise have the funds to engage in legitimate litigation against an well-funded adversary?

That said, there seems to be an inherent unfairness in a system where the opponent with the largest coffers wins, and your only reasonable option as a litigant is to find an equally capable financer to invest in your redress of grievances.

In the US, it depends on the jurisdiction.

See here:

http://en.wikipedia.org/wiki/Champerty_and_maintenance