The algorithm the credit agencies use does not know how to deal with investors that have 30 or 40 mortgages.  

Here are some links that may describe some of these issues:http://seattlebubble.com/blog/2013/09/16/zillow-trulia-still-apathetic-about-data-quality/If you were also relying on any type of zillow estimate or anything that in some way relied on or utilized the 'zestimate', then that really might be a problem as anything with a 'zestimate' in it is often not only way off in some cases, they often literally revise the algorithm which does often mean revising their historical estimated data.http://blog.louisgray.com/2011/06/zillow-rewrites-home-price-history.htmlZillows response on this is also somewhat of concern:This is directly from Zillow:Do you ever change prior Zestimates?

Also, with the many changes Google makes to their ranking algorithm, one of my sites had their rank drop so I started paying higher per lead, so I had to refine some things with onsite SEO and that corrected it and actually made some leads cheaper.

I used to advertise on Facebook but they continue to change their algorithm.

Do they have some special some special algorithm that can give them such accuracy on their "Zestimate" like Google uses in it's search advertisements? 

All of these things are strange algorithms that credit reporting agencies use to create your score.

Google has extensively changed their algorithms over the last few years placing other factors as much higher value ie, unique/powerful content, powerful back links related in your niche, Key-worded appropriately (1-3%/keyword/page) ect.  

Zillow says their algorithms are within 7% of value's.

In search engine algorithms, it actually might be a compliment - other people think your content is worthy of copying.

In some cases, metered water bills could be cheaper than flat rate if the algorithm of flat rate doesn't fit the property.