I'm not going to deny the value of patents. They do incentivise invention, and I'm cool with that, but too much patent power, and you actually do the opposite.
Since DisKamper has already covered the monopoly problem, I'll go over others. There's nothing wrong with rounded corners in phones being patented, but medical patents are, in particular, a serious issue. Many third-world citizens in disease-stricken nations are denied access to essential medicine for survival because of the increased patent prices. AIDS is a good example. In India, patients can still buy first-line drugs at reasonable prices, but the second-line drugs are unreasonably priced because they are protected by TRIPS. South Africa also tried importing generics from Brazil and India, which was seriously delayed as they were caught up in a lawsuit against pharmaceutical transnationals who accused them of violating TRIPS.
The global enforcement of patent protection also widens the global income gap because developing countries are simply not in the position to enforce them. India is a famous example - both their economy and their people rely heavily on generics, which are generated by reverse-engineering medicine by large pharmaceutical companies. With the implementation of TRIPS, it's estimated that there's been a $20 billion redistribution of wealth from developing nations to developed ones.
Medical patents also disincentivise the invention of drugs for diseases of poverty, such as sleeping sickness. Under patent protection, medicine companies gain far more from medicines aimed at diseases of affluence than at diseases of poverty.
Apart from medical patents, agricultural patents are another serious problem. I'm sure most people are already familiar with the injustices faced by farmers who used GM seeds. They must continue to buy the patented seeds from transnationals like Monsanto since switching to GMO isn't reversible. Seed saving is strictly prohibited and the practice may lead to legal sanctions. Occasionally, it has even been reported that farmers must switch to GMO because wind blew seeds to their fields.
Another problem with plant patents is biopiracy. Some corporations from developed nations are learning traditional agricultural practices from developing nations, then passing them as their own to get patents. Although a few lawsuits against them have been won, remember that most victims do not have the legal savoir-faire or the financial means to win a lawsuit against multinational giants.
I know the argument that patents have time restrictions. Well, they do, but evergreening is a practice ever-so-prevalent. They can easily extend their patent by modifying the product slightly, just enough to pass off as original.
There should thus be far more restrictions on patents. We could set a cap on how much the corporations can earn before the patent is revoked, so it acts as enough of a financial incentive but at the same time protects the rights of consumers after a while. For medical patents in developing nations, I might even suggest abolishing product patents altogether, and keeping only process patents. (exceeded word limit, continue below)
Some may argue that patents provide an incentive to innovate. However, there are other incentives to come up with new ideas like prizes. Consumers can pool their money together to create a prize for the company that can create the product they want. This is already happening with websites like Kickstarter, and such websites will only increase in the future.
Patents tend to create monopolies and increase barriers to entry in markets. This only further widens the income gap. Restricting patents would allow small companies to more easily work off the innovations of others, and increase market competition, leading ultimately to more innovation and lower prices.
Patents should have a time limit as they do now. Medical patents should have far fewer years. All should not be able to sit on a patent and collect money from people who knowingly or inadvertently use (patent trolls). Anyone who patents something should sell it within two years or patent should be opened with limited (perhaps 3% of profit) royalty of use. In the event of pandemic and patent is on cure or treatment, the president or Congress should have the right to order creation of cure without royalties (eminent domain for goods).
I am an aspiring inventor. I invent a cool new device. I patent said device. I then make money off of that device. Because of how awesome it is, someone else decides to use that device *gasp* without paying me. Is it fair to me for someone else to use my creation to make money without me getting a piece of the action?
Tl;dr I make device. I sell device. Someone else uses my R&D for their own, to even the playing field, rendering my efforts useless, as they just take it and possibly undercut me. Because they are more established or something, they manage to undercut me, and I lose out on my own work.
A non-example is here.
A world without patents is a world with less innovation, because there is less incentive to do it, because they know that their ideas will be immediately given to other people, who already have money, and can produce the products more cheaply. If anything, it will cause information to shrink, as people and corporations alike jealously guard their tech to prevent being undercut.
Reverse-engineering will run rampant, and it will be completely unstoppable, because there is no patent in place to protect the tech.
Eventually, there will be enough plausible deniability for everyone to simply price-fix under similar systems, and nothing short of routine reverse-engineering under a local regulatory body or a bunch of collaborating journalists would be able to prove a thing.
In short, everything would be shot to hell.
The music industry? Well, copyrights are kinda patents... Ditto for the publishing industry. Basically, all intellectual property would become public domain. Kiss entire industries goodbye if patents cease to exist.
Crowds can decide specifics on what they want, but they need a kick in the pants from a corporation whose marketing department utterly failed to read them to get them clamoring for X.