In the following video, Fool analysts Blake Bos and Austin Smith discuss three reasons that investors in Waste Management might consider selling the stock.

Investors need to stay aware of changing trends that affect the amount of trash people generate, Blake says, including a trend toward greener products.

With current economic conditions, Waste Management may also be bumping up against its ceiling in terms of what it can charge cash-strapped municipalities for waste disposal, Austin says.

Investors should keep an eye on Waste Management's push to mine its own own resources for energy, such as natural gas. This strategy leaves the company more susceptible to commodity price changes and could potentially shrink margins.

Lastly, Waste Management's position as dominant market leader puts it in an almost monopoly-like position but also restricts its potential avenues for growth.

See more in the following video.

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