I suppose there's always danger of overdoing anything, but the very reason I recommend street-performance is that you're more likely to do *more* singing, and to be sure of making yourself heard, than in the privacy of your room (or your acoustically-ideal bathroom).

My theory is that performing out on the streetcorner for extended lengths of time can help a novice singer "settle in" to a more relaxed and natural process than he/she can achieve either when practicing privately and quietly, or when performing in a highly self-conscious situation for a brief period of time (e.g., floor spot, open mike, etc.)

On the street, once you get over the initial "stage" fright, you can become blissfully unconscious of your various detailed worries and find yourself singing more naturally than ever before. At least, that's how I remember it happening for me quite a few years ago.