"Files and folders, therefore, are encrypted with symmetric encryption. Symmetric encryption means the same key is used to encrypt and decrypt your data; this is less secure than asymmetric encryption (where one key encrypts and a different key decrypts), but it's faster and easier to implement."
I just saw that and facepalmed as well. Beyond the sheer number of attacks you can perpetrate on RSA versus AES (never mind in the browser), MEGA is using 2048-bit RSA, which has a 112-bit security level, versus 128-bit AES.
Symmetric ciphers are used almost exclusively for the encryption of large files. They're more secure, faster, and easier to work with.
"Files and folders, therefore, are encrypted with symmetric encryption. Symmetric encryption means the same key is used to encrypt and decrypt your data; this is less secure than asymmetric encryption (where one key encrypts and a different key decrypts), but it's faster and easier to implement."