Have your tried iSpot?

I was driving back from a trip to the woods when I heard a programme on BBC Radio 4 describing iSpot here. It seems quite an interesting and useful project. A typical query might be to submit a picture similar to the above with a brief description. "This weed has invaded my garden in recent years and manages to grow where there is little soil in crevices. Please can you tell me what it is?" Can anyone here tell me what it is?