OK... HOA fees and Mello-Roos taxes - like apples and oranges.
HOA fees are fees that are charged, usually monthly, by your HOA. The HOA is a nonprofit association that manages the community. If you're in an attached condo, they also own the structure. They typically own the parks, maintain the landscape, run programs (e.g. holiday parties), and enforce the CC&Rs.
Mello-Roos, or Community Facilities Districts, are districts of lots of homes where the voters have elected* to tax their parcels in order to pay P&I on bonds, the revenue of which will pay for a project to benefit the district. For example, near Beckman High, the residents are subject to a parcel tax that pays the bonds that were issued to raise the money to buy the land for and construct the school.
HOA fees can go up or down, depending on your HOA, their budget, and their reserves.
CFDs should stay stable over time and then stop after the bonds are paid off. The reason CFDs are called Mello-Roos, is because the two legislators that sponsored the legislation that allowed for the formation of CFDs and the issuance of CFD bonds were Mello and Roos. Typically, the financial model will allow for a few deadbeats so that the parcel taxes won't go up and/or the bonds won't default. Also, upon nonpayment of taxes, not only can the CFD record a tax lien, they can foreclose on the house to pay the tax bill. I had a friend who ran a business placing the liens and foreclosing on them in the IE during the last downturn.
*In new developments, the voters in the election are those who own the land, typically only the developer. Thus, for Orchard Hills, likely the only voter for those bonds, was TIC. Proposition 13 does not allow for the imposition of new parcel taxes without a 55% (for schools) or 2/3 (for other projects) vote. Given the anti-tax sentiment, the best way to assure that the project gets the streets, schools, etc. that the developer wants, is to form the district and hold the vote prior to selling the lots and homes.