Something tells me you are either using a version of MySQL prior to 5.0, you called an older version of mysqldump, or you messed with the settings of the dump.
What usually blows up a mysqldump past the size of its dataset is the option --skip-extended-insert.
In older versions of MySQL, there was no extended insert. That means each and every row in a table had an INSERT command to itself. If a table had 2,000 rows, the mysqldump output will have 2,000 INSERT commands. That's a whole lot of commas, parentheses, single quotes, and "INSERT INTO" tags to place in a dump file.
In newer versions of MySQL, --extended-insert was added to group together dozens (or even hundreds) of rows in a single INSERT. SO, instead of...
INSERT INTO tbname VALUES (1);
INSERT INTO tbname VALUES (2);
INSERT INTO tbname VALUES (3);
INSERT INTO tbname VALUES (4);
INSERT INTO tbname VALUES (5);
You could have this:
INSERT INTO tbname VALUES (1),(2),(3),(4),(5);
For mysqldump, --opt includes --extended-insert. If you use --skip-opt when doing mysqldump, it disables --skip-extended-insert. Here are the options of mysqldump that affect extended insert:
Use multiple-row INSERT syntax that include several
(Defaults to on; use --skip-extended-insert to disable.)
--opt Same as --add-drop-table, --add-locks, --create-options,
--quick, --extended-insert, --lock-tables, --set-charset,
and --disable-keys. Enabled by default, disable with
Run these at the Linux command line
If these do not match the version of mysql you are running on the server, or multiple versions of MySQL exist on the same machine, get that straightened out. Until then, make sure you call the correct version of mysqldump and don't use --skip-opt.