Per the Virgin Mobile website:
"Mobile ID is a free service from Virgin Mobile that lets you download a complete mobile experience on demand. Customize your phone to match whatever you're into... music, entertainment, social networking, and more.
Each Mobile ID pack includes a unique set of specially-selected apps, ringtones, wallpapers, and widgets - all in a single, easy-to-install package. Start with our exclusive Virgin Mobile ID and load up your phone with a hand-picked collection of mobile must-haves. Or, choose from other great Mobile ID packs created by content experts like MTV and E!.
Mobile ID packs are free to download and easy to swap. Just tap the ID icon on your phone's main screen to get started. Load as many as 5 ID packs onto your phone at once. You can switch between them whenever you want with just a few clicks."
It is useless Virgin Mobile /Sprint bloatware as far as I am concerned and I do not use it. I am not rooted and do not know what the consequences are if you do remove it after rooting your phone.
I hope this answers your question. Good Luck!