This merino wool scarf is supposedly to be dry cleaned, but some people told me it can be washed in machine (wool program). Anyone knows more about this?
Dry clean only labels are attached to clothing to minimize the liability of the clothing manufacturers against damage to clothing due to being improperly cleaned and/or washed. Clothing owners would sue manufacturers for changes of size, loss of buttons, and other trivial issues. The legal "fix" was to refuse responsibility for after-purchase care with the label "notice."
Wool should be washed in only cool water and air dried. Do not use heat to dry wool quickly as it will allow the wool to shrink.
EDIT: I'd suggest washing something small like your scarf by hand in a bowl (bathroom sink). Use a MILD cool/cold water detergent, appropriate for washing wool, that you can find in a large market. Then, gently press the extra water from the last rinse out of the scarf. Don't twist or wring the water out.
It'll take less time than the machine will.
Either way, you'll end up with your scarf needing to dry out. Air dry it flat so it won't stretch on a towel or a rack with a mesh shelf to allow the air to circulate.