There are already such careers underway in Europe, especially England. They have, of course, failed to spot most of the asteroids that have whizzed by close until 3 days after the event.
In any case, spotting asteroids won't do any good at all unless there is a program to actually do something about such asteroids. That is the problem: there is no action plan. Put anti-asteroid hardware in space and don't wait until the last minute.
And you've gotta wonder, if they didn't spot so many of them coming, how many did really they spot going? I'd be willing to bet they completely missed many, either coming or going.
If today's mapping programs have any great value, imo, it'll be to spark interest in programs that someday can actually do something to prevent collisions.