Much of the underlying technology involved is hidden from the public and the competition, but they could emulate and simulate to provide similar results if they so wished. In many cases they already do this, or come close to it.

In one example[0], an online retailer was taken to court by Amazon for using a one-click buy button. Having all of the customer's billing and shipping information on hand already, this feature is obvious and makes sense for any online retailer, but Amazon has patented it. The competing retailer's solution was to add a confirmation page, increasing it to two clicks but providing similar convenience.

[0]: http://en.wikipedia.org/wiki/1-Click#Barnes_.26_Noble

Edit: Added a link to the referenced case

I think it really depends on what you mean by "technology", but if you mean PageRank, I assume it is really a math/algorithm description (I've never read the patent), so it would no longer be considered patentable.

That said, it seems like everyone uses some variant on PageRank as at least part of their search engine heuristics, so it might be that the patent is fairly narrow and/or they don't try to enforce it anyways.

Is not most of it still under trade secret?

To answer your question, yes.

Would ending software patents hinder Google's ability to compete effectively? I don't think so. Patents are not where the competitive action is.