according to topic:
http://www.zabbix.com/forum/showthread.php?t=23309

1K = 1024 or 1K = 1000 ?? -> let's stop making people guess

==== 1 === (FAST FIX)
if item unit is B - displayed units suffixes should be:

• KiB
• MiB
• GiB
• etc

http://en.wikipedia.org/wiki/IEEE_1541

=== 2 === (Improvement)
imo it's good idea to add additional option in item creation/edit form

so people can chose display format:

• normal (k, M, G, ... = x 1000)
• binary prefixes (Ki, Mi, Gi, ... = x 1024)
• unixtime - translated to "yyyy.mm.dd hh:mm:ss"
• uptime - translated to "hh:mm:ss" or "N days, hh:mm:ss"
• s - translated to "yyy mmm ddd hhh mmm sss ms"
• as it is (like rpm % ect)

but additional column in items table is needed so it can be only target for zabbix 2.0
(i can't see any db updates related witch new versions in 1.8.x line)

now u can use Unist field and do it this way (temporary):

If set, Zabbix will add the unit postfix to all received values.
Till Zabbix 1.8.2, default multiplier is 1024, and some units have special processing:
b, bps - 1000 is 1K, special processing for bits.
Since Zabbix 1.8.2, default multiplier is 1000, and special processing is used for units B, where multiplier is 1024.
For example, if units are set to B, Zabbix will display:
1 as 1B
1024 as 1KB
1536 as 1.5KB

+ Since Zabbix 1.8.8, default multiplier is 1000, and special processing is used for units iB and ib, where multiplier is 1024.
+ For example, if units are set to iB, Zabbix will display:
+ 1 as 1B
+ 1024 as 1KiB
+ 1536 as 1.5KiB

unixtime - translated to "yyyy.mm.dd hh:mm:ss"
uptime - translated to "hh:mm:ss" or "N days, hh:mm:ss"
s - translated to "yyy mmm ddd hhh mmm sss ms", parameter is treated as number of seconds. Only 3 upper major units are shown, like "1m 15d 5h" or "2h 4m 46s". If there are no days to display, only two levels are displayed - "1m 5h" (no minutes, seconds or milliseconds are shown). Will be translated to "< 1 ms" if the value is less than 0.001.

EDIT:
and triggers
i have one defined like this:
used bandwidth is to high:

{switch:if.Fa5.In.last(0)}>3.9M

i don't know - its activating when used bandwidth is over 3.9*1024*1024 ? or 3.9*1000*1000

but server should calculate it like this:

{switch:if.Fa5.In.last(0)}>3.9M -> {switch:if.Fa5.In.last(0)}>3.9*1000*1000
{switch:if.Fa5.In.last(0)}>3.9Mi -> {switch:if.Fa5.In.last(0)}>3.9*1024*1024

ADDITIONAL INFO (don't read if u don have time):
i have TS3 server and its statistics are in attachment

packets are in units x1000
all transfers in unist x1024
all is clear no one need to guess