You can put this with nice image/grapics of serrated/non-serrated leaves. This idea remind me of Akinator, where you can answer Yes, Proabbly, Don'tKnow, ProbablyNot, No. (http://en.akinator.com/ ) (You also have to consider the possibility of a mistake in one of the answers.)
One problem is that plants have different names in different parts of the word, or even in different parts of the same country. Another problem is that the same name may describe different plants in different places. (Perhaps the Wikipedia article can be the "official" identifier.)
Well, in botany is more a question of: "are the leaves entire, serrulate, serrate, double serrate, dentate, crenulate, crenate, toothed, spiny or undulated?". A lot of people just will walk away when things go a little hard, probably feeling cheated. The problem is that people are just lazy.
I can probably identify thousands of genus plants at least at first sight but is not easy and sometimes is impossible. There are about 3000 spurge species for example (and maybe ten real specialists in the genus Euphorbia in the entire world).
There are also some legal troubles in the field to care for. Some typical recurrent doubts in plant identification in my experience are:
1-"How can I cultivate peyote/cannabis/some ilegal drug in my house?, Is this a male or female plant? Is this cactus in my public park a San Pedro?"
2-"Is this leaf/mushrom/berry that I'm cooking edible or poisonous? (typically with a blurry small photo of some green poor thing that falls between a child in cucumber disguise and an alligator)."
Both 1 and 2 situations could easily escalate to a lawsuit against you. Assure you to put a big disclaimer note in the terms of use.
3-"Urgent!, Urgent!, I want you to do my schoolwork. Identify my entire herbarium, Is for yesterday!."
This guy will not even remember to thank you later most of the times, nor will consider to paid a cent for this (I will gladly charge him for my time if I could otherwise).
You can put this with nice image/grapics of serrated/non-serrated leaves. This idea remind me of Akinator, where you can answer Yes, Proabbly, Don'tKnow, ProbablyNot, No. (http://en.akinator.com/ ) (You also have to consider the possibility of a mistake in one of the answers.)
One problem is that plants have different names in different parts of the word, or even in different parts of the same country. Another problem is that the same name may describe different plants in different places. (Perhaps the Wikipedia article can be the "official" identifier.)