You can delete any Yahoo! ID from your Messenger List by sending a text message in the following format:

del (their Yahoo! ID)

For example, type:

del dairyman88

Depending on your carrier, send the command from your mobile phone to:

All (Supported) U.S. Wireless Carriers—92466
Rogers—92466000
All (Supported) India Wireless Carriers—8242
TMTouch—1777
Maxis—32235
SMART—2580
GLOBE—22580
M1—8881
DTAC—192466
TELKOMSEL—4246
EXCELCOM—9246
STARHUB—0903