You can't send tasks to other users of MLO, as far as I know, but there are ways to tag a task to note that it's assigned to another person.
Some people set up categories or flags with people's names. My personal way is to assign a category called @WaitingFor and then put the person's name at the top of my note, tagged with a question mark (eg "?Jim Smith"). I'm thinking of starting to use the Text Tag to record the responsible person's name, instead - The advantage being that MLO prompts me with a list of text tags I've already used. I'll see how that goes.
Stéphane