What are the disadvantages of Google Wallet?

Could you elaborate on the downsides of using Google Wallet? I'm interested in understanding the potential challenges or limitations one might encounter while utilizing this digital payment service. For instance, are there any concerns regarding privacy or security? Are there transaction fees that could become a burden for frequent users? Additionally, is it compatible with all types of devices and merchants, or are there limitations in terms of usage? I'd appreciate it if you could provide a concise yet comprehensive overview of the disadvantages associated with Google Wallet.