Around here, the blackberry is regarded as a terrible pest, to be sprayed and destroyed at all cost (the cost being the health of the sprayer and their family and the environment....). We try and do our bit to keep pests down etc, and we try and get the blackberries out of the native vegetation, as they can be a little dominating over revegetation. But to us blackberries are also a really valuable resource.
Blackberries at this time of year (mid-late summer) are in full fruit. As an example, this morning we spent maybe 30mins or so, and picked nearly 2kg of berries, and got to enjoy a nice walk while we were at it. In the supermarket blackberries sell for at least $5 per 250g punnet.... (hmm, the 2kg of blackberries simmering on the stove would make a pretty expensive jam.... we live a pretty luxurious life!)
Blackberries are fodder for stock - we keep goats and goats LOVE blackberries (horses like the fruit, alpacas the young shoots). I think that they would be happy to only eat blackberries for their entire lives! Bees love the blackberry flowers - so for bee keepers they are also important (fingers crossed the bees will happen this year).
Blackberries are medicinal. The leaves can be used to make an ezcema remedy, and the berries (eaten) are a pregnancy tonic among other things (Raspberry leaf tea is normally drunk during pregnancy - and raspberries and blackberries belong to the family Rubus). There are specific remedies that use blackberry, read up on it in one of the many herbal books around - I recommend Juliette de Bairacli Levy, who has written on herbs for both humans and animals.
Hmmm, now I present you a pest, probably far more damaging to the garden than the humble blackberry....
This young man has discovered the art of pulling up carrots! Yes, the carrot patch that I am so proud of, my very first successful carrot patch..... I think there might have to be a child proof fence put up around the bed, or else we will only be eating very very tiny carrots!!!