On several of the sites I've worked on (mylifetime.com, fastcompany.com, incbiznet.com) we've had two problems with views cache.
- Views serialized cache data being too large for MySQL's max_packet_size
- Views unserialized cache data being too large for memcached's hard 1MB chunk limit
So I finally made a patch of the fix I implemented splitting the table cache into 4 queries to get around the issues. The first issue can be fixed by changing max_packet_size to a larger number, but the second is a hard limit of memcached by default. You can compile it to have a larger chunk size but then you waste memory and have a slower lookup time.
Here is the patch.