I would have to argue that this is beyond stupid....(but as a Republican I think it's great)
Well the advantages of yard signs are huge, first and foremost it is a way to get people involved in the race, contrary to what folks who are politically active think not everyone who wants to help your candidate by phone banking and walking. Some just want a sign. A sign that will get their neighbors thinking, a sign that may start a conversation with the guy next door who is undecided.
Secondly, it is an opening to get signs for candidates down ticket up in someones yard. Oh, you want an Obama sign sure we can do that any chance we can give a Bill Jones for State Rep sign as well? They help down ticket because they are a gateway to get signs for lesser known candidates. It can provide names that can be used for other elections, hey you took an Obama sign in November can we give you a Jones for Mayor sign for the April election? They help build lists.
Third, it just seems cocky not to do it. They may be cliche' and I have said 'yard signs don't vote' more than a few times myself, but they do get people involved for not a whole lot of money. People expect them and feel slighted if you don't find them worthy, don't underestimate that especially if you have people calling you elitist.
Finally your candidates candidacy is historic, people are going to want something to remember that, take advantage of that.
Then again you obviously know what you are doing....