Anyone that's used/written algorithms knows they need to be run natively on your machine/server to run the fastest. Calling a web service will slow this down greatly.
If this site was turned into a marketplace of code listed for each algorithm that can automatically translate between languages, I could see it going somewhere.
I'm not sure what value they're providing, exactly. Anyone can put algorithms on the web now: you write them in a standard language like PHP and upload them to any hosting service.
I imagine you ship off the data, let them run the algorithm, and they return the results. This has no effect on the Big-O efficiency of the algorithm; the only additional cost is a simple roundtrip of the data.
I'm failing to see how that's so different from ex. running an intense algorithm in a worker thread.
Although the algorithms may run efficiently, ferrying significant amounts of data to and from a web service could quickly negate any gains.