Just added this to the wiki 

http://wiki.apache.org/cassandra/FAQ#dropped_messages

Cheers

-----------------
Aaron Morton
Freelance Cassandra Developer
@aaronmorton

On 6 Aug 2011, at 10:53, Philippe wrote:

Hi,
I see lines like this in my log file
 INFO [ScheduledTasks:1] 2011-08-06 00:51:57,650 MessagingService.java (line 586) 358 MUTATION messages dropped in server lifetime
 INFO [ScheduledTasks:1] 2011-08-06 00:51:57,658 MessagingService.java (line 586) 297 READ messages dropped in server lifetime
 INFO [ScheduledTasks:1] 2011-08-06 00:51:57,658 MessagingService.java (line 586) 4696 RANGE_SLICE messages dropped in server lifetime

How worried should I be ?
Are they reported as timeout exceptions on the client ?

Thanks