Apart from what the others have said I think you could have difficulty removing the plants from the tin if they become somewhat pot bound.
Root trainers are designed with this in mind.
Apart from that and the fact you will use a lot of compost I see no reason why you cant!
But I will stick to my 70mm square pots which are quite cheap providing you buy in bulk
see here;
http://tinyurl.com/2j5j4z they are £32.40 for 1500
When I bought mine about 10 years ago, I bought 4000 at around 1p each and sold them to people in our garden club and Chrysant & Dahlia society.
I kept around 2000 for myself and they are still going strong, I just washed over 800 of them on Tuesday last