if you start slowly, and make sure the hot liquid cascades down the sides evenly (vs just letting it fill from the bottom up while the top portion is still cold) you shouldnt have problems. obviously be careful, and there is always a possibility of something going bad. you might want to put the carboy in a bucket if you are doing this in your kitchen or something.
people who do the no-chill method of brewing dump the beer, post-boil, directly into a carboy when its 190+ degrees. ive done it before with no mishaps. if you just fill it from the bottom without warming the whole thing evenly, the temperature gradient is probably not a good thing.