How to backup MS SQL Server databases off-site?
I'm not sure I would advocate it as a good solution, neither performance wise nor as a best practice, but there actually is a possibility.

In short, the steps would  be 


Make a backup on a swap file on the server
Create a temporary table with a varbinary field
Insert the backup into the table
Fetch column data using ADO.NET
Save the stream in a file


The full source code is available on codeplex Transferring backup files from a remote SQL Server instance to a local machine without network shares, FTP, HTTP

The gist of the code is:

Step 1:

_sql = String.Format("BACKUP DATABASE {0} TO DISK " + 
       "= N'{1}\\{0}.bak' WITH FORMAT, COPY_ONLY, INIT, " + 
       "NAME = N'{0} - Full Database Backup', SKIP ", 
       _dbname, AremoteTempPath, _dbname);
_command.CommandText = _sql;
_command.ExecuteNonQuery();


Step 2: 

_sql = String.Format("IF OBJECT_ID('tempdb..##{0}') IS " + 
                     "NOT NULL DROP TABLE ##{0}", temporaryTableName);
_command.CommandText = _sql;
_command.ExecuteNonQuery();
_sql = String.Format("CREATE TABLE ##{0} (bck VARBINARY(MAX))", 
                     temporaryTableName);
_command.CommandText = _sql;
_command.ExecuteNonQuery();


Step 3:

_sql = String.Format("INSERT INTO ##{0} SELECT bck.* FROM OPENROWSET" + 
       "(BULK '{1}\\{2}.bak',SINGLE_BLOB) bck", 
       temporaryTableName, AremoteTempPath, _dbname);
_command.CommandText = _sql;
_command.ExecuteNonQuery();


Step 4 &amp; 5:

_sql = String.Format("SELECT bck FROM ##{0}", temporaryTableName);
SqlDataAdapter da = new SqlDataAdapter(_sql, _conn);
DataSet ds = new DataSet();
da.Fill(ds);
DataRow dr = ds.Tables[0].Rows[0];
byte[] backupFromServer = new byte[0];
backupFromServer = (byte[])dr["bck"];
int aSize = new int();
aSize = backupFromServer.GetUpperBound(0) + 1;

FileStream fs = new FileStream(String.Format("{0}\\{1}", 
                AlocalPath, fileName), FileMode.OpenOrCreate, FileAccess.Write);
fs.Write(backupFromServer, 0, aSize);
fs.Close();


The original code was written by Adrian Pasik under the bsd license and published on codeplex.