Hi,
Itaian accommodation has only been deregulated these last few years which is why there is now an abundance of B and B's and Locanda's.
Broadly speaking they fall into 2 categories "Residenza Epoch" which is a B and B offered in a/private villa or Palazzo call it what you will with some historical interest.
www.villadellapergola.it is a good example of this category. We stayed there in September and it was a super experience. My review is on this site but there is also a link on the information pages which explains this new to Italy idea better than I'm doing here.
The second type are "Locandas". Similar to the old Pensione's they offer a good standard of accommodation but none of the facilities of a hotel so you can expect a good room and breakfast only. We stayed in a very good example of this in Campiglia above the Cinque Terre, Locanda Tramonti and again that was a very good experience. Unfortunately their website is down but I will post as soon as it's up again. Here breakfast supplies were provided and you made your own in the kitchen.
As Sally said prices are good in this type of B and B. If you check out the reviews page you will notice Locanda Barnaba in Venice which will give you an idea of what you can expect.In between these two categories you can expect to find accommodation in "ordinary" private homes.
Hope I haven't confused you too much.. !
I'm sure someone else knows better than me.
All are subject to much rigorous control and inspections by the state,as you might expect.
Wendy