I have had a few occurrences with people who have given my babies (10 month old b/g twins) food without asking first:

One instance was someone who saw a bottle of formula on the counter and just started feeding my son, who was 2 months old at the time--I was wanting to EBF, but the formula was there to supplement, if needed. I hadn't needed to use it, and just left it on the counter, so I was annoyed with the person who decided to feed my son because: a) I was using formula as a last-resort & b) it was left out for awhile and could've gone bad.

Another person was holding my dd and gave her a french fry while I was not in the room. I was upset when I returned to see dd with the fry, because I didn't want her having all that salt; at the time, she wasn't familiar with finger foods, so I was also concerned about her choking, since the feeder was not watching dd eat. I did speak up and tell the person not to feed dd the french fry, and I asked her to take it from dd, but it was clear that the person felt that I was being unreasonable.

Is it unreasonable to expect people to ask the parent of an infant LO if they can give LO food? Also, how would you go about handling a similar situation?