Whats the advantages and disadvantages of stringers as a source of news?

It totally depends on the organization using them. The sleazy gossip rags probably would not confirm info and the freelance people could be expected to lie or write implying things just to sell an article. First rate news sources use them but have standards.

"Reuters, like many news organisations, uses freelance journalists to supplement its network of staff journalists. We use “stringers” in places where the flow of news is not sufficient to justify the presence of a staff correspondent, in countries where the authorities may not allow Reuters to assign a staff journalist or to cover stories of a specialist nature when we do not have the necessary expertise among our own staff.
We also occasionally use ad-hoc stringers for individual stories and assignments.

Hiring stringers

Utmost care must be taken in hiring stringers that we use reputable journalists who are able and willing to adhere to our rigorous standards of accuracy, objectivity, sourcing and freedom from bias. No individual correspondent should hire a stringer without the explicit approval of the bureau chief or editor in charge. We must exercise the utmost caution in hiring ad-hoc stringers for individual stories.
Preference in hiring stringers should be given to professional journalists whose skills meet our standards. Bureaus should not hire non-journalists as stringers without the explicit approval of the regional managing editor and the relevant specialist editor. Under no circumstances should we hire officials of a government or local authority, members of the armed forces or police and intelligence services or public relations employees to work as stringers.
Stringers must be briefed on our standards of accuracy, objectivity, sourcing and freedom from bias. Regular stringers should be asked to read an abridged version of our Code of Conduct and editorial guidelines. Bureau chiefs should have these documents. Stringers should be asked to acknowledge that they have read the contents and agree to abide by them.
All stringers must be told at the hiring stage that Reuters reserves the right to rewrite the material they provide to ensure that it meets our standards and style and to insert material from other reporters as well as background and context to ensure that their reports are suitable for a global readership. Stringers must be told that Reuters expects to use their byline and be given an opportunity to discuss circumstances when this might not be appropriate.
Training can be offered to stringers who contribute regularly. Such training is at the discretion of the bureau chief and the regional managing editor. Remuneration for stringers will depend on local and individual circumstances. There will be cases of sensitivity where it could be dangerous for a stringer’s identity to be revealed because of possible pressure from a government or another employer. In such cases the identity of a stringer should not be divulged to the authorities, members of the public or any third party outside Reuters without explicit approval from a senior editor, who will escalate as appropriate. It should be normal practice, however, for stringers to identify themselves as working on behalf of Reuters. They should not misrepresent themselves.

Handling material from stringers

Bureaus and desks that handle copy or verbal reports from stringers must expect the same standards of accuracy, objectivity, sourcing and freedom from bias as they do from staff. However, because stringers may be less accountable than staff, particular caution must be exercised. Here are some guidelines:

Apply the “smell” test. A fact or quote may look fine, but does it “smell” right? If not, challenge the stringer to provide more information. If a fact or quote raises a question in your mind, it will probably jar with the reader too.
Beware of anonymous sources, such as unnamed officials or diplomats, especially if you are not familiar with the stringer’s work.
Insert only relevant background and context into a stringer report, as you would with a staff journalist’s report. Extraneous background and context, especially if it is contentious, may get the stringer into trouble with authorities and may get Reuters into trouble with the stringer.
Be cautious about using stringer bylines on stories that are contentious, contain sensitive material or come from datelines where identifying the stringer may expose the stringer to problems with the authorities. Be aware which stringers are comfortable having their bylines used and which are not, whether because of sensitivities with the authorities or with their primary employer.
Never add a byline to a stringer story without consulting the stringer, a staff correspondent on the ground, the bureau chief or a specialist editor.
Preference should always be given to staff coverage of a diarised news story of significant interest, unless the bureau or desk is entirely satisfied that the particular stringer will do as good a job. On major breaking news, staff coverage must be ensured as rapidly as possible unless there are very strong grounds for continuing with stringer coverage alone. Consult your manager if in doubt.
Apply the same byline policy to stringer copy as to staff copy. When a desk or bureau makes significant changes to the thrust or structure of a bylined news story that is reported or written primarily by the bylined journalist, it will make reasonable efforts to send the story back to the correspondent for a final check. If the journalist cannot be reached in good time, the senior editor on the appropriate filing desk determines whether the story should be issued with the byline or whether it should be removed. Where a byline is used to signal our presence at a dateline, additional reporting names and locations and the name of the writer must be listed at the end of the story as appropriate.
Never “ghost” a news story under the byline of a stringer who has contributed nothing to the report. Never “ghost” a news analysis under a stringer’s byline.
When in any doubt about a stringer story after performing the above checks, consult your manager."