Not neccesarily. All this means is that buyers have more of a preference for TradeHill and sellers prefer Mtgox. When consider that long term bitcoin miners tend to be sellers and newbies tend to be buyers, this is a good sign for TH (new adopters, without prior bias, are choosing it over Mtgox). Ultimately the most important sign is volume and there TH is still behind (1/6 of Mtgox at the time of writing).