Most technologies go through a stage when everything seems possible. Personal computers in the early 1980s, the internet in the late 1990s and mobile apps around the beginning of this decade were like that.

But so was the first unboxing of a Galaxy Note 7. In time, either suddenly or gradually, reality sets in.

The internet of things still looks promising, with vendors and analysts forecasting billions of connected devices that will solve all sorts of problems in homes and enterprises. But the seams are starting to show on this one, too. As promising as the technology is, it has some shortcomings. Here are a few.

Bad data

IoT systems are only as good as the data they capture, and some of it is .

, the Broadband Internet Technical Advisory Group warned in a report issued late last year.

last year when its DVRs and connected cameras got pulled into a Mirai botnet that took down large parts of the internet. Weak default passwords opened them up to the attack. The company had stopped shipping units with those weak passwords the year before, but for older products it was reduced to asking owners to update the firmware and change the password by hand.

This means two things: IoT devices attract hackers, because they’re plentiful and overlooked, and it’s up to vendors to build in security and allow for automatic over-the-air updates.

Changing technology

IoT is still a moving target, and it will be for a while yet. That makes it hard to choose technologies, because some may not survive for the long haul.

If you’re a consumer, orphaned products like Nest’s hub can feel like a ripoff and an inconvenience. If you’re an enterprise with millions of sensors built for a network that’s fallen out of favor, maintenance and migration could be very expensive.

Some specifications that are only a few years old, like , are already merging. Having fewer standards is probably a good thing, and vendors will try to make the old work with the new, but consolidation may still hold surprises.

raise this issue, too. There are many to choose from now, but analysts say there probably won’t be enough of a market for all in the long run. While the towers might not come down before it’s time to replace the devices that use them, a network in survival mode won’t be expanding, either. So for now, it’s best to proceed with caution.

You can’t just plug it in

Connecting a bunch of machines and suddenly getting automation and business insights sounds great, but IoT doesn’t work that way.

Because it crosses the line between computing systems and physical infrastructure, like machine tools and air conditioners, IoT forces IT to collaborate with operations people they may not even know. In fact, a Technalysis survey last year found operations departments were in charge of IoT projects than IT shops.

And while pilot projects are a good way to start, by each department keep enterprises from getting all the benefits of IoT, Strategy Analytics found in a survey last year. Data collection projects need to go hand in hand with analytics, including knowing what questions to ask and which tools can answer them. Haste can cause more confusion than convenience: Fifty-one percent of enterprises Strategy Analytics surveyed weren’t sure whether IoT was paying off.