Of course ordinary citizens can use bitcoins. But, the catch is that, they will not be able to use it properly unless they have atleast some knowledge about cryptography and security. A lot of terms used in the community will leave them confused. But, the thing is that anyone can learn something if it is an interest or a necessity. Just look at computers 
Well i think anyone could used bitcoin as long as you have the resources and some knowlege in the technology now, and at first it is the terms/words are hard to understand and I start writing them and did some research in order to understand bitcoin. And if someone is really interested with bitcoin they will really invest thier time to read,and study about bitcoin.