it is almost always better for the motor to warm up a motor before use.
here are some reasons (not all)
1 the oil is cold and not flowing as freely as when hot.
2 metal expands as it gets hotter, the clearances of the parts in the motor may not be at the optimum clearance until it is hot.
3 on many motors the fuel mixture will be optimum when hot.
4 some motors it wont cause much (if any) problems, other motors it can cause big problems (on my snowmobile i have wiseco pistons, if you dont warm it up first you can cause a cold seizure).
can you start it up cold and run at full throttle??? yes you can.
could it cause long term or short term problems??? yes it can.
if you want to keep it forever let it warm up, and use synthetic oil if it is air cooled (the reason for the synthetic oil is if the motor ever over heats the oil wont break down).
if you get a new one every year or dont care just run it like you stole it.