MS SQL Server 2008 R2 network backup
I believe you can. We backup to a network location although we have the location mapped to a drive. 

It seems you can use a UNC as well though according to this answer http://social.msdn.microsoft.com/Forums/sqlserver/en-US/965cd9c4-f4d5-4492-a202-f09b78d89ed1/how-to-backup-a-database-to-a-network-drive?forum=sqltools. 

Have a look at the answer as there's some good considerations on here like if the sql service login has access to the network location.