UKBA do state that:-
"All supporting documents must be originals, not copies."
Also:-
Every personal bank or building society statement should clearly show:
your name or your sponsor's name
the account number
the date of the statement
the financial institution's name and logo
transactions covering the recent period
that there are enough funds present in the account to support a dependent partner and any dependent children
If you want to send electronic bank statements from an online account, these must contain all of the details listed above. You will also need to send a supporting letter from your bank, on headed paper, confirming that the statements are genuine. Alternatively, electronic bank statements with the official stamp of the bank that issued the statements will be accepted. The stamp must appear on every page of the statement.
We will not accept statements that simply show the balance in the account on a particular day, as these documents do not show that there are consistent funds to meet the maintenance requirement.
As lastlid said some people have only submitted scanned copies without issue.
It's a personal choice, but if you want to minimise risk and a shed load of money it's better to follow the rules.